measuring densities of solids and liquids using magnetic
TRANSCRIPT
S1
Measuring Densities of Solids and Liquids Using Magnetic Levitation
Fundamentals
SUPPORTING INFORMATION
Katherine A Mirica Sergey S Shevkoplyas Scott T Phillips Malancha Gupta
and George M Whitesides
Department of Chemistry amp Chemical Biology Harvard University Cambridge MA 02138
Corresponding author E-mail gwhitesidesgmwgroupharvardedu
S2
General Methods
The NdFeB magnets (5 cm times 5 cm times 25 cm) were purchased from KampJ Magnetics
(wwwkjmagneticscom) and aligned on top of one another 45 cm apart within aluminum
blocks Similar magnets can also be obtained from Applied Magnets wwwmagnet4lesscom at
a lower price The strength of the magnetic field within the device was measured using a hand-
held DC magnetometer (AlphaLab Inc wwwtrifieldcom) Calibrated density standards (plusmn
00002 gcm3 at 23degC) were purchased from American Density Materials (Stauton VA
wwwdensitymaterialscom) Spherical polymer samples were purchased from McMaster-Carr
(wwwmcmastercom) Polystyrene microspheres with precisely defined radii were supplied by
Duke Scientific Corporation (wwwdukescientificcom) Polysciences Inc
(wwwpolysciencescom) and Spherotech (wwwspherotechcom) All other samples and
reagents were purchased from Sigma Aldrich (Atlanta GA) and used without further
purification ldquoLevitation heightrdquo of samples was measured using a ruler with millimeter-scaled
marking Helium pycnometery measurements were performed by Quantachrome Instruments for
a fee on an Ultrapyc 1200e instrument
S3
Figure S0 A plot generated using numerical simulation using COMSOL Multiphysics showing
the dependence of the z-component of the magnetic field Bz on the separation between magnets
(d) for d = 25 35 45 55 65 75 mm along the centerline between the two magnets
S4
Figure S1 Photographs demonstrating levitation of a glass bead (density = 11500 plusmn 00002
gcm3) in different aqueous paramagnetic solutions (1M MnCl2 1M MnBr2 1M CuSO4 1M
GdCl3 1M FeCl2)
MnCl2 MnBr2 CuSO4 GdCl3 FeCl2
10 m
m
S5
Figure S2 Net Volumetric Magnetic Susceptibilities of Common Diamagnetic Substances1-7
-50x10-4
-40x10-4
-30x10-4
-20x10-4
-10x10-4
00
10x10-4
20x10-4
30x10-4
Net
Volu
me M
agne
tic S
usceptibili
ty (
SI
unitle
ss)
diamagnetic substance
hem
oglo
bin
DN
A
alb
um
in
chole
stero
l
aceto
ne
eth
anol
ben
zene
chlo
roben
zene
eth
ylene g
lycol
wate
r
dic
hlo
rom
eth
ane
chlo
rofo
rm
gly
cero
l
PM
MA
silic
on
pol
ysty
rene
pol
yeth
ylene
teflon
silic
a
sodiu
m c
hlo
ride
zinc
lead
dia
mond
silv
er
gol
d
indiu
m
pyr
oly
ticgra
phite
(|| axi
s)
gra
phite
rod
bis
muth
meta
l
pyrolytic graphite
( axis)
S6
Figure S3 Deliberate misalignment of the container with the centerline between the magnets
(red dotted line) Beads of different densities (from top to bottom 10500 10800 11000
11200 11500 gcm3) levitating in 1M MnCl2 align with the centerline between the magnets
regardless of the position of the container as long as the centerline is accessible within the
container (A and B) Inability of the beads to align with the centerline (C and D) does not result
in significant change in the levitation height of the beads Scale bar represents 10 mm
A
B
C
D
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S2
General Methods
The NdFeB magnets (5 cm times 5 cm times 25 cm) were purchased from KampJ Magnetics
(wwwkjmagneticscom) and aligned on top of one another 45 cm apart within aluminum
blocks Similar magnets can also be obtained from Applied Magnets wwwmagnet4lesscom at
a lower price The strength of the magnetic field within the device was measured using a hand-
held DC magnetometer (AlphaLab Inc wwwtrifieldcom) Calibrated density standards (plusmn
00002 gcm3 at 23degC) were purchased from American Density Materials (Stauton VA
wwwdensitymaterialscom) Spherical polymer samples were purchased from McMaster-Carr
(wwwmcmastercom) Polystyrene microspheres with precisely defined radii were supplied by
Duke Scientific Corporation (wwwdukescientificcom) Polysciences Inc
(wwwpolysciencescom) and Spherotech (wwwspherotechcom) All other samples and
reagents were purchased from Sigma Aldrich (Atlanta GA) and used without further
purification ldquoLevitation heightrdquo of samples was measured using a ruler with millimeter-scaled
marking Helium pycnometery measurements were performed by Quantachrome Instruments for
a fee on an Ultrapyc 1200e instrument
S3
Figure S0 A plot generated using numerical simulation using COMSOL Multiphysics showing
the dependence of the z-component of the magnetic field Bz on the separation between magnets
(d) for d = 25 35 45 55 65 75 mm along the centerline between the two magnets
S4
Figure S1 Photographs demonstrating levitation of a glass bead (density = 11500 plusmn 00002
gcm3) in different aqueous paramagnetic solutions (1M MnCl2 1M MnBr2 1M CuSO4 1M
GdCl3 1M FeCl2)
MnCl2 MnBr2 CuSO4 GdCl3 FeCl2
10 m
m
S5
Figure S2 Net Volumetric Magnetic Susceptibilities of Common Diamagnetic Substances1-7
-50x10-4
-40x10-4
-30x10-4
-20x10-4
-10x10-4
00
10x10-4
20x10-4
30x10-4
Net
Volu
me M
agne
tic S
usceptibili
ty (
SI
unitle
ss)
diamagnetic substance
hem
oglo
bin
DN
A
alb
um
in
chole
stero
l
aceto
ne
eth
anol
ben
zene
chlo
roben
zene
eth
ylene g
lycol
wate
r
dic
hlo
rom
eth
ane
chlo
rofo
rm
gly
cero
l
PM
MA
silic
on
pol
ysty
rene
pol
yeth
ylene
teflon
silic
a
sodiu
m c
hlo
ride
zinc
lead
dia
mond
silv
er
gol
d
indiu
m
pyr
oly
ticgra
phite
(|| axi
s)
gra
phite
rod
bis
muth
meta
l
pyrolytic graphite
( axis)
S6
Figure S3 Deliberate misalignment of the container with the centerline between the magnets
(red dotted line) Beads of different densities (from top to bottom 10500 10800 11000
11200 11500 gcm3) levitating in 1M MnCl2 align with the centerline between the magnets
regardless of the position of the container as long as the centerline is accessible within the
container (A and B) Inability of the beads to align with the centerline (C and D) does not result
in significant change in the levitation height of the beads Scale bar represents 10 mm
A
B
C
D
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S3
Figure S0 A plot generated using numerical simulation using COMSOL Multiphysics showing
the dependence of the z-component of the magnetic field Bz on the separation between magnets
(d) for d = 25 35 45 55 65 75 mm along the centerline between the two magnets
S4
Figure S1 Photographs demonstrating levitation of a glass bead (density = 11500 plusmn 00002
gcm3) in different aqueous paramagnetic solutions (1M MnCl2 1M MnBr2 1M CuSO4 1M
GdCl3 1M FeCl2)
MnCl2 MnBr2 CuSO4 GdCl3 FeCl2
10 m
m
S5
Figure S2 Net Volumetric Magnetic Susceptibilities of Common Diamagnetic Substances1-7
-50x10-4
-40x10-4
-30x10-4
-20x10-4
-10x10-4
00
10x10-4
20x10-4
30x10-4
Net
Volu
me M
agne
tic S
usceptibili
ty (
SI
unitle
ss)
diamagnetic substance
hem
oglo
bin
DN
A
alb
um
in
chole
stero
l
aceto
ne
eth
anol
ben
zene
chlo
roben
zene
eth
ylene g
lycol
wate
r
dic
hlo
rom
eth
ane
chlo
rofo
rm
gly
cero
l
PM
MA
silic
on
pol
ysty
rene
pol
yeth
ylene
teflon
silic
a
sodiu
m c
hlo
ride
zinc
lead
dia
mond
silv
er
gol
d
indiu
m
pyr
oly
ticgra
phite
(|| axi
s)
gra
phite
rod
bis
muth
meta
l
pyrolytic graphite
( axis)
S6
Figure S3 Deliberate misalignment of the container with the centerline between the magnets
(red dotted line) Beads of different densities (from top to bottom 10500 10800 11000
11200 11500 gcm3) levitating in 1M MnCl2 align with the centerline between the magnets
regardless of the position of the container as long as the centerline is accessible within the
container (A and B) Inability of the beads to align with the centerline (C and D) does not result
in significant change in the levitation height of the beads Scale bar represents 10 mm
A
B
C
D
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S4
Figure S1 Photographs demonstrating levitation of a glass bead (density = 11500 plusmn 00002
gcm3) in different aqueous paramagnetic solutions (1M MnCl2 1M MnBr2 1M CuSO4 1M
GdCl3 1M FeCl2)
MnCl2 MnBr2 CuSO4 GdCl3 FeCl2
10 m
m
S5
Figure S2 Net Volumetric Magnetic Susceptibilities of Common Diamagnetic Substances1-7
-50x10-4
-40x10-4
-30x10-4
-20x10-4
-10x10-4
00
10x10-4
20x10-4
30x10-4
Net
Volu
me M
agne
tic S
usceptibili
ty (
SI
unitle
ss)
diamagnetic substance
hem
oglo
bin
DN
A
alb
um
in
chole
stero
l
aceto
ne
eth
anol
ben
zene
chlo
roben
zene
eth
ylene g
lycol
wate
r
dic
hlo
rom
eth
ane
chlo
rofo
rm
gly
cero
l
PM
MA
silic
on
pol
ysty
rene
pol
yeth
ylene
teflon
silic
a
sodiu
m c
hlo
ride
zinc
lead
dia
mond
silv
er
gol
d
indiu
m
pyr
oly
ticgra
phite
(|| axi
s)
gra
phite
rod
bis
muth
meta
l
pyrolytic graphite
( axis)
S6
Figure S3 Deliberate misalignment of the container with the centerline between the magnets
(red dotted line) Beads of different densities (from top to bottom 10500 10800 11000
11200 11500 gcm3) levitating in 1M MnCl2 align with the centerline between the magnets
regardless of the position of the container as long as the centerline is accessible within the
container (A and B) Inability of the beads to align with the centerline (C and D) does not result
in significant change in the levitation height of the beads Scale bar represents 10 mm
A
B
C
D
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S5
Figure S2 Net Volumetric Magnetic Susceptibilities of Common Diamagnetic Substances1-7
-50x10-4
-40x10-4
-30x10-4
-20x10-4
-10x10-4
00
10x10-4
20x10-4
30x10-4
Net
Volu
me M
agne
tic S
usceptibili
ty (
SI
unitle
ss)
diamagnetic substance
hem
oglo
bin
DN
A
alb
um
in
chole
stero
l
aceto
ne
eth
anol
ben
zene
chlo
roben
zene
eth
ylene g
lycol
wate
r
dic
hlo
rom
eth
ane
chlo
rofo
rm
gly
cero
l
PM
MA
silic
on
pol
ysty
rene
pol
yeth
ylene
teflon
silic
a
sodiu
m c
hlo
ride
zinc
lead
dia
mond
silv
er
gol
d
indiu
m
pyr
oly
ticgra
phite
(|| axi
s)
gra
phite
rod
bis
muth
meta
l
pyrolytic graphite
( axis)
S6
Figure S3 Deliberate misalignment of the container with the centerline between the magnets
(red dotted line) Beads of different densities (from top to bottom 10500 10800 11000
11200 11500 gcm3) levitating in 1M MnCl2 align with the centerline between the magnets
regardless of the position of the container as long as the centerline is accessible within the
container (A and B) Inability of the beads to align with the centerline (C and D) does not result
in significant change in the levitation height of the beads Scale bar represents 10 mm
A
B
C
D
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S6
Figure S3 Deliberate misalignment of the container with the centerline between the magnets
(red dotted line) Beads of different densities (from top to bottom 10500 10800 11000
11200 11500 gcm3) levitating in 1M MnCl2 align with the centerline between the magnets
regardless of the position of the container as long as the centerline is accessible within the
container (A and B) Inability of the beads to align with the centerline (C and D) does not result
in significant change in the levitation height of the beads Scale bar represents 10 mm
A
B
C
D
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S7
Figure S4 Effect of tilting the experimental set-up on height at which the objects levitate A)
Photographs of beads of different density (from top to bottom 10500 10800 11000 11200
11500 gcm3) levitating in 1 M MnCl2 at different values of tilt angle θ The dimensions of the
container in which the beads levitate are 50 mm times 30 mm times 45 mm The container spans the
entire width and height of the magnets and is centered lengthwise between the magnets B)
Images in shown in panel A rotated by angle θ to emphasize the effect of tilting on the levitation
height of the beads
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
A
B
θθθθ = 0deg 5deg 9deg 15deg 20deg 40deg 60deg
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S8
Figure S5 Photographs of polystyrene spheres of different radii levitating at t0 in aqueous 500
mM MnCl2 Spheres of R gt ~ 7 microm form well defined clusters at h spheres of ~ 2 microm lt R lt ~ 7
microm form diffuse clouds centered around h while spheres of R lt ~ 2 microm remain essentially
uniformly dispersed throughout the solution
R (micromicromicromicrom) = 76 51 38 15
5 1
0
15
2
0
25 3
0 m
m
z
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S9
Sources and Magnitude of Errors for Calculating Densities of Objects Using Eqn (8)
Experimental parameters and constants B0 d g c and T
We measured the magnitude of the magnetic field at the center on the surface of the
bottom magnet with a magnetometer and found that in the configuration shown in Fig 1a 0B
was (0375 plusmn 0003) Tesla
The distance between the two magnets d remained constant in our experiments and was
equal to (45 plusmn 05) mm
The acceleration due to gravity g at the surface of the Earth ranges from 978 ndash 982
ms2 where the exact value depends on the latitude and other factors we used the average value
of 980 ms2 in our calculations and neglected this variation in our error analysis The typical
variation in g does not constitute a significant source of uncertainty in calculation of density
using eqn 8
We measured T using a thermometer with an accuracy of plusmn 1 degC
We did not measure c directlymdashinstead we calculated it (eqn S0A) based on the mass
of the salt m (g) measured using an analytical balance with accuracy of 31010 minustimes=mδ g (as
specified by the manufacturer of the analytical balance) the total volume of solution V (L)
measured using a volumetric flask with accuracy of 310080 minustimes=Vδ L (as specified by the
manufacturer of the volumetric glassware) and the molecular weight of the salt M (gmol) as
provided by the vendor We estimated the error associated with our calculation of concentration
cδ using eqn (S0B)8 and found it to be less than plusmn 0002 M for the range of concentrations we
used in this study
mc
MV= (S0A)
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S10
2 2
2
1 mc m V
MV MVδ δ δ = + minus
(S0B)
Magnetic Susceptibility of the Medium m
χ
The magnetic susceptibility of the suspending mediumm
χ depends on concentrations
and magnetic properties of all the species present in solution We calculated mχ using eqn (S1)
in which p
χ is the molar magnetic susceptibility of the paramagnetic salt (m3mol units of SI) c
is the concentration of the paramagnetic salt (molL) and 6109 minustimesminus is the bulk magnetic
susceptibility of water9 10
The dependence of the molar magnetic susceptibilities of the
paramagnetic salt p
χ on temperature follows the Curie-Weiss law given by eqn (S2) where T is
the temperature of the medium (expressed in ordmK) CW
C is the Curie constant (m3 K mol) and θ
is the Weiss constant (ordmK) of the paramagnetic salt10
The dependence of magnetic susceptibility
of the medium on temperature is then given by eqn (S3) in which we assumed that the magnetic
properties of water do not change significantly with temperature1 2
69 10m pcχ χ minus= minus times (S1)
CWp
C
Tχ
θ=
minus (S2)
69 10CWm
Cc
Tχ
θminus= minus times
minus (S3)
In eqns (S1 S3) we neglected the contribution of the magnetic properties of gasses
dissolved in the suspending medium For example air-saturated water at room temperature
contains up to 03 mM of dissolved O2 gas ( 61034492
minustimes=molar
Oχ )1 11
mdash the contribution of O2 to
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S11
the magnetic susceptibility of the medium is 2
813 10Oχ minus= times which is at least three orders of
magnitude less than typical values of m
χ
Density of the Paramagnetic Solution ρm
The dependence of density of the medium mρ on the concentration of paramagnetic salt
in solution and on temperature of the solution is given by eqn (S4) where T is expressed in ordmC
( )W
Tρ is the density of pure water ( 0 99965W = 1
1 20438 10Wminus= times 2
2 61744 10Wminus= minus times ) and
AndashF are empirical dimensional parameters specific to the paramagnetic salt (for GdCl3
2105382 times=A 1101491 minustimesminus=B 3103861 minustimes=C 1103061 minustimesminus=D 0E = and 0F = for
MnCl2 2100221 times=A 1109664 minustimes=B 2103071 minustimesminus=C 0106593 minustimesminus=D
1106311 minustimesminus=E and 3107744 minustimes=F )12
2 3 2 3 2 3 2 2
3 2 2 3 2 3 2 3 2 2
0 1 2
( ) ( )m W
T c T Ac BcT CcT Dc Ec T Fc T
W W T W T Ac BcT CcT Dc Ec T Fc T
ρ ρ= + + + + + + =
= + + + + + + + + (S4)
Magnetic Susceptibility of the Sample χs
The typical values of sχ for diamagnetic substances are temperature-independent small
(about 6 61 10 10 10minus minusminus times minus times ) and vary little from substance to substance (see Fig S2 for typical
values of magnetic susceptibilities of common substances)1 2 9
We neglected these differences
in calculations of densities based on the empirical estimates of α and β (eqn 8) from the
calibration curves For the measurements of density via the direct application of eqn (8) we set
6105 minustimesminus=sχ (in the middle of the typical range of values of sχ for most diamagnetic
substances Fig S2) and estimated the accuracy of this assumption as 510s
δχ minus= (unitless)
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S12
This type of oversimplification and the estimation of uncertainty may not be general for
all cases especially when strongly diamagnetic (| sχ | gtgt 10-5
) or slightly paramagnetic samples
are levitated In such cases either an accurate value of sχ should be used when calculating
densities of eqn (8) or a larger margin of error assumed for this type of density measurement 13
Levitation Height h
We measured the levitation heights of objects h using a rulermdashwe estimate the precision
of this measurement to be plusmn05 mm
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S13
Error Analysis
To estimate the error of our measurements of density using the calibration curves we
assume that we know parameters α and β in eqn (8) exactly and consider sρ to be a function
of only one variable h we use eqn (S5) to propagate the uncertainty in h for these types of
measurements8 In eqn (S5) α is the calibration parameter from eqn (8) and hδ is plusmn 05 mm
ss
dh h
dh
ρδρ δ αδ= = (S5)
To estimate the error associated with the direct use of eqn (8) for measuring the density
we treat sρ as a function of several independent variables 0B d sχ T c and h each of
which is a source of independent random error (eqn S6)8 (Notice that
mρ and
mχ are not
independent parameters ndash they are calculated from T and c using eqns (S4) and (S3)
respectively)
2 22 2 2 2
0
0
s s s s s ss s
s
T c h d BT c h d B
ρ ρ ρ ρ ρ ρδρ δ δ δχ δ δ δ
χ part part part part part part = + + + + + part part part part part part
(S6)
Eqn (S7) summarizes eqn (8) and eqns (S3) and (S4) in a form convenient for
calculating the partial derivatives in eqn (S6)
2 2
0 0
2
3 2 2 3 2 3 2 3 2 2
0 1 2
6
4( ) 2( )
( )
9 10
s m s ms m
o o
m
CWm
B Bh
g d g d
where
T c W W T W T Ac BcT CcT Dc Ec T Fc T
Cc
T
χ χ χ χρ ρ
micro micro
ρ
χθ
minus
minus minus= + minus
= + + + + + + + +
= minus timesminus
(S7)
The partial derivates of m
ρ and m
χ with respect to T and c are needed for estimating
eqn (S6) and are given below (eqns S8A-B)
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S14
( ) 2
1 2 3 2 3 2
1 2
32 2
2
mCW
m
C c TT
W W T Bc CcT Ec Fc TT
χθ
ρ
minuspart= minus minus
partpart
= + + + + +part
(S8A)
2 1 2 1 2 2 1 23 3 3
2 2 2
m CW
m
C
c T
A BT CT Dc ETc FT cc
χθ
ρ
part=
part minuspart
= + + + + +part
(S8B)
The partial derivatives of s
ρ with respect to 0B d sχ T c and h are given by eqns
(S9A-F) below
( )
2
0
2
2
1 2 3 2 3 2
1 2
4
2
32 2
2
s m m
o
mCW
m
B dh
T g d T T
where
C c TT
W W T Bc CcT Ec Fc TT
ρ χ ρmicro
χθ
ρ
minus
part part part = minus minus + part part part
part= minus minus
partpart
= + + + + +part
(S9A)
2
0
2
2 1 2 1 2 2 1 2
4
2
3 3 3
2 2 2
s m m
o
m CW
m
B dh
c g d c c
where
C
c T
A BT CT Dc ETc FT cc
ρ χ ρmicro
χθ
ρ
part part part = minus minus + part part part
part=
part minuspart
= + + + + +part
(S9B)
2
0
2
4
2
s
s o
B dh
g d
ρχ micro
part = minus part (S9C)
2
0
2
4( )s s m
o
B
h g d
ρ χ χmicro
part minus=
part (S9D)
( )2
2 302( )4s s m
o
Bd hd
d g
ρ χ χmicro
minus minuspart minus= minus
part (S9E)
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S15
02
0
8( )
2
s s m
o
dh B
B g d
ρ χ χmicro
part minus = minus part (S9F)
Finally to estimate the error s
δρ in the measurement of density of the sample s
ρ one
needs to substitute the expressions for the partial derivatives (eqns S9A-F) into eqn (S6) and
evaluate the resulting expression using the values of parameters 0B d sχ T c and h and
the tolerances of these parameters 0Bδ = plusmn 0003 (T) dδ = plusmn 05 times 10-3
(m) sδχ = plusmn 10-5
(unitless) Tδ = 1 (degK) cδ = plusmn 0002 (M) and hδ = plusmn 05 times 10-3
(m) respectively We provide
two examples of successful application of this procedure below
Dependence of sδρ on Tδ
We use eqn (S6) (and eqns (S9A-F)) to compare the effect of the uncertainty in
temperature (plusmn 1 degC vs plusmn 10 degC) on the accuracy of the measurement of density of polystyrene
spheres levitating in 350 mM solution of MnCl2 This type of estimate may be appropriate for a
user in a remote location with no immediate access to a thermometer for measuring temperature
For simplicity we assume that all temperature-independent parameters and the value of 0B are
known exactly Table S1 summarizes the parameters used for and the result of this estimation
Dependence of sδρ on 0Bδ
Similarly we use eqn (S6) (and eqns (S9A-F)) to compare the effect of 0Bδ = plusmn 0003 T
(typical accuracy established by using a magnetometer) vs 0Bδ = 01 T (a safe assumption for
variation between NdFeB magnets supplied by various manufacturers) on the accuracy of the
density measurement of polystyrene spheres levitating in 350 mM MnCl2 For simplicity we
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S16
assume that all parameters except 0Bδ are known exactly Table S2 summarizes the parameters
used for and the result of this estimation ndash while the uncertainty in the measurement of density
increases significantly from plusmn 00002 to 0008 gcm3 the measurement of density is still fairly
accurate and may be useful in less demanding situations
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S17
Table S0 Densities common plastics and organic liquids that can be used as density standards
in magnetic levitation
sample density (gcm3)
organic polymers
high-density polyethylene 097
polydimethylsiloxane (PDMS) 104
polystyrene 105
poly(styrene-co-acrylonitrile) 108
poly(styrene-co-
methylmethacrylate)
114
nylon 66 114
polymethylmethacrylate 118
polycarbonate 122
neoprene rubber 123
polyethylene terephthalate
(mylar)
140
polyvinylchloride (PVC) 140
cellulose acetate 142
polyoxymethylene (delrin) 143
polyvinyledene chloride 170
polytetrafluoroethylene
(Teflon)
220
organic liquids
3-fluorotoluene 0997
2-fluorotoluene 1004
fluorobenzene 1025
3-chlorotoluene 1072
chlorobenzene 1107
24-difluorotoluene 1120
2-nitrotoluene 1163
nitrobenzene 1196
1-chloro-2-fluorobenzene 1244
13-dichlorobenzene 1288
12-dichlorobenzene 1305
dichloromethane 1325
3-bromotoluene 1410
bromobenzene 1491
chloroform 1492
1-bromo-4-fluorobenzene 1593
hexafluorobenzene 1612
carbon tetrachloride 1630
tetradecafluorohexane 1669
25-dibromotoluene 1895
perfluoro(methyldecalin) 1950
iodomethane 2280
tribromomethane 2890
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S18
Table S1 Dependence of uncertainty in measurement of density sδρ on uncertainty in Tδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T known exactly known exactly
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC plusmn 1 degC plusmn 10 degC
c Concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 plusmn 00003 gcm
3 plusmn 00026 gcm
3
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00003 gcm
3 plusmn 0003 gcm
3
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S19
Table S2 Dependence of uncertainty in measurement sδρ on ucertainty in 0Bδ
Parameter P Description Magnitude of P Pδ Pδ
experimental parameters
0B strength of magnetic
field at the surface of
the magnet
0375 T plusmn 0003 T plusmn 01 T
d distance between
magnets
45 mm known exactly known exactly
T Temperature 23 degC known exactly known exactly
c concentration of MnCl2 0350 M known exactly known exactly
Unknowns
sχ bulk magnetic
susceptibility of the
sample
-5 times 10-6
(SI unitless) known exactly known exactly
calculated parameters
)( Tcmρ density of
paramagnetic medium
10339 gcm3 known exactly
known exactly
)( Tcmχ bulk magnetic
susceptibility of the
medium
plusmn 56 times 10-6
known exactly known exactly
constants
g acceleration due to
gravity
980 ms2 na na
micro0 permeability of free
space
4π times 10-6
NA-2
na na
independent variable
h ldquolevitation heightrdquo of
the sample above the
bottom magnet
120 mm known exactly known exactly
dependent variable
sρ density of sample 10483 gcm3 plusmn 00002 gcm
3 plusmn 0008 gcm
3
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S20
Table S3 Linear correlations for h and ρs at different concentrations of MnCl2 obtained from
the plot of these two parameters in Fig 5A
concentration of
MnCl2(M)
linear least squares fit
to Fig 5A
least squares linear fit
in the form of Eqn 8 α β
01 h = -3664ρs + 3717 ρs = -00003h + 10145 -00003 10145
05 h = -449ρs + 493 ρs = -0002h + 1098 -0002 1098
10 h = -247ρs + 294 ρs = -0004h + 1190 -0004 1190
15 h = -160ρs + 206 ρs = -0006h + 1287 -0006 1287
20 h = -117ρs+ 162 ρs = -0008h + 1385 -0008 1385
25 h = -934ρs + 138 ρs = -0011h + 1478 -0011 1478
30 h = -808ρs + 126 ρs = -0012h + 1559 -0012 1559
Figure S6 Dependence of α and β on [MnCl2] A) Plot correlating α with [MnCl2] least
squares linear fit y = 00041x - 00001 R2
= 0997 B) Plot correlating β with [MnCl2] least
squares linear fit y = 01889x + 10014 R2
= 0999
00000
00020
00040
00060
00080
00100
00120
00140
000 100 200 300 400
[MnCl2]
αα αα
080
090
100
110
120
130
140
150
160
170
000 100 200 300 400
[MnCl2]
ββ ββ
A
B
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S21
Table S4 Details of experimental parameters used for obtaining densities of solids using
calibration curves in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
h
(mm)
calibration curve used Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 167 plusmn 05 37173664 +minus= sh ρ 10099 plusmn 00002
ρ = 11000 gcm3 1000 220 plusmn 05 294247 +minus= sh ρ 1101 plusmn 0002
ρ = 11500 gcm3 1500 219 plusmn 05 206160 +minus= sh ρ 1152 plusmn 0003
spherical polymers
polystyrene 0500 235 plusmn 05 493449 +minus= sh ρ 1047 plusmn 0001
nylon 66 1000 135 plusmn 05 294247 +minus= sh ρ 1137 plusmn 0002
polymethylmethacrylate 2000 233 plusmn 05 162117 +minus= sh ρ 1186 plusmn 0004
irregularly-shaped
polymers
polystyrene 0500 220 plusmn 05 493449 +minus= sh ρ 1049 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 281 plusmn 05 294247 +minus= sh ρ 1076 plusmn 0002
poly(styrene-co-
methylmethacrylate)
1000 140 plusmn 05 294247 +minus= sh ρ 1133 plusmn 0002
organic droplets
chlorobenzene 1000 185 plusmn 05 294247 +minus= sh ρ 1115 plusmn 0003
2-nitrotoluene 1000 52 plusmn 05 294247 +minus= sh ρ 1169 plusmn 0003
dichloromethane 3000 195 plusmn 05 126880 +minus= sh ρ 1324 plusmn 0006
3-bromotoluene 3000 125 plusmn 05 126880 +minus= sh ρ 1405 plusmn 0006
chloroform 3000 65 plusmn 05 126880 +minus= sh ρ 1479 plusmn 0007
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S22
Table S5 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in MnCl2 Table 2 compares the calculated densities from Tables S3-S5
Sample [MnCl2]
(molL)
Density of
MnCl2
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0100 10081 10 times 10
-6 167 plusmn 05 1010 plusmn 0001
ρ = 11000 gcm3 1000 10994 177 times 10
-6 220 plusmn 05 1101 plusmn 0002
ρ = 11500 gcm3 1500 11486 270 times 10
-6 219 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0500 10492 84 times 10-6
235 plusmn 05 1047 plusmn 0001
nylon 66 1000 10994 177 times 10-6
135 plusmn 05 1134 plusmn 0003
polymethylmethacrylate 2000 11971 363 times 10-6
233 plusmn 05 1191 plusmn 0005
irregularly-shaped
polymers
polystyrene 0500 10492 84 times 10-6
220 plusmn 05 1050 plusmn 0001
poly(styrene-co-
acrylonitrile)
1000 10994 177 times 10-6
281 plusmn 05
1078 plusmn 0003
poly(styrene-co-
methylmethacrylate)
1000 10994 177 times 10-6
140 plusmn 05
1132 plusmn 0003
organic droplets
chlorobenzene 1000 10994 177 times 10-6
185 plusmn 05 1115 plusmn 0002
2-nitrotoluene 1000 10994 177 times 10-6
52 plusmn 05 1166 plusmn 0005
dichloromethane 3000 12923 548 times 10-6
195 plusmn 05 1329 plusmn 0007
3-bromotoluene 3000 12923 548 times 10-6
125 plusmn 05 1416 plusmn 0007
chloroform 3000 12923 548 times 10-6
65 plusmn 05 1488 plusmn 0008
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S23
Table S6 Details of experimental parameters used for obtaining densities of solids using eqn (8)
in GdCl3 Table 2 compares the calculated densities from Tables S3-S5
Sample [GdCl3]
(molL)
Density of
GdCl3
solution
(gcm3)
mχ
(unitless)
h
(mm) Calculated sρ
(gcm3)
glass beads
ρ = 10100 gcm3 0050 10100 8times 10
-6 260 plusmn 05 1009 plusmn 0001
ρ = 11000 gcm3 0400 10950 125times 10
-6 202 plusmn 05 1102 plusmn 0002
ρ = 11500 gcm3 0600 11426 192times 10
-6 205 plusmn 05 1152 plusmn 0003
spherical polymers
polystyrene 0200 10468 58 times 10-6
228 plusmn 05 1046 plusmn 0001
nylon 66 0400 10950 125 times 10-6
86 plusmn 05 1136 plusmn 0004
polymethylmethacrylate 0750 11780 242 times 10-6
213 plusmn 05 1185 plusmn 0003
irregularly-shaped
polymers
polystyrene 0140 10321 38 times 10-6
85 plusmn 05 1045 plusmn 0003
poly(styrene-co-
acrylonitrile)
0250 10589 75 times 10-6
127 plusmn 05
1076 plusmn 0003
poly(styrene-co-
methylmethacrylate)
0530 11260 168 times 10-6
209 plusmn 05
1132 plusmn 0002
organic droplets
chlorobenzene 0500 11189 158 times 10-6
277 plusmn 05 1100 plusmn 0003
2-nitrotoluene 0500 11189 158 times 10-6
122 plusmn 05 1157 plusmn 0003
dichloromethane 1500 13514 493 times 10-6
262 plusmn 05 1300 plusmn 0007
3-bromotoluene 1500 13514 493 times 10-6
178 plusmn 05 1404 plusmn 0006
chloroform 1500 13514 493 times 10-6
118 plusmn 05 1471 plusmn 0006
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S24
Figure S7 Plots showing the dependence of error in sρ on various experimental parameters at
constant temperature A) Dependence of sδρ on [MnCl2] in water at 23 degC Dependence of sδρ
on h over the entire vertical distance between the magnets (45mm) at B) 01 M MnCl2 and C)
50 M MnCl2 at 23 degC
0000
0005
0010
0015
0020
0025
0 5 10 15 20 25 30 35 40 45
h (mm)
δρ
δρ
δρδρ
s
0
0001
0002
0003
0004
0005
0006
0 5 10 15 20 25 30 35 40 45
h (mm)
δρδρ δρδρ
s
0000
0005
0010
0015
0020
0 1 2 3 4 5 6 7
[MnCl2] (molL)
δρδρ δρδρ
s
combined
δρ
δρ
δρ
δρ
δρ
δρ
)(combinedsδρ)( ms ρδρ)( ms χδρ)( ss χδρ)( 0Bsδρ
)(dsδρ)(hsδρ
A
B
C
01 M MnCl2
50 M MnCl2
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs
S25
References
(1) Lide D R Ed CRC Handbook of Chemistry and Physics 89th
ed [Online] CRC Press
Boca Raton FL 2008
(2) Du Tremolet de Lacheisserie E Gignoux D Schlenker M Eds Magnetism Kluwer
Academic Publishers Norwell MA 2002
(3) Hirota N Kurashige M Iwasaka M Ikehata M Uetake H Takayama T
Nakamura H Ikezoe Y Ueno S Kitazawa K Physica B 2004 346 267-271
(4) Ikezoe Y Kaihatsu T Sakae S Uetake H Hirota N Kitazawa K Energy Conv
Manag 2002 43 417-425
(5) Kang J H Choi S Lee W Park J K J Am Chem Soc 2008 130 396-397
(6) Kuchel P W Chapman B E Bubb W A Hansen P E Durrant C J Hertzberg
M P Concepts in Magn Reson 2003 18A 56-71
(7) Simon M D Geim A K J Appl Phys 2000 87 6200-6204
(8) Taylor J R An Introduction to Error Analysis University Science Books Sausalito
CA 1997
(9) Andres U Magnetohydrodynamic amp Magnetohydrostatic Methods of Mineral
Separation John Wiley amp Sons New York NY 1976
(10) Hatscher S Schilder H Lueken H Urland W Pure Appl Chem 2005 77 497-511
(11) Weiss R F Deep-Sea Research 1970 17 721-735
(12) Sohnel O Novotny P Densities of Aqueous Solutions of Inorganic Substances
Elsevier New York NY 1985
(13) Paramagnetic samples will also levitate in this device provided that χm gt χs