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6-1966

Tellurium (VI): Polarography and polyolcomplexesPeter T. KissingerUnion College - Schenectady, NY

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Recommended CitationKissinger, Peter T., "Tellurium (VI): Polarography and polyol complexes" (1966). Honors Theses. 1940.https://digitalworks.union.edu/theses/1940

TILLURltJM (VI): POtAtlOCIAPHY AND POLYOL COMPLEXES

by

Peter Thomae Kissinger c/c 116 6 II;

Senior Thesis Submitted

in Partial Fulfillment

of the Requirements for Graduation

DEPARTMENT OF CHEMISrRY

UNION COLLEGE

MAY 1966

c , z

)1

This The is

/} Submitted by

td.:z:~ d • '

to the

Department of Chemistry of Union College

in partial fulfillment of the requl~ementa of the degree of

Bachelor of Science with a Major in Chetnistry

ie approved by

ii

"The cbyroiat.s are a strange class of mortals impelled by a.n almost inat.ne impulse to seek their pleasure atnQng smoke and vapour, soot and flame, poieon& and poverty; yet among all these evils 1 se~ to live so sweetly. that may I die if l would change places with the Persian Kin.g .. 0 ( 1)

iii

Ht5TORICAL DACKGllOUND AND GENERAL lNTRODUCTION ••

POLYOL-TET.JDBATE COMPUtXES • • • • • • • • • • • •

PO?AllOGRAPHt • • • • • • • • • • • • • POIAROGMPUIC lNV!STlGATI.ON OF TELWRIUM (VI) AND PO.LYO!rORTROmLUJRATBS • •••••••

' '

• • • • • • • MEDIA • • • • • .• , • • • • • • • • " .... CONCENTRATION STUDY. • • • • • • • . . . . •· . VARIATION or MEB.CtflY HEAD "

EtlCTllOCAPlUAll.Y DATA •••

• • • • • • • • •

• • • • • • •

VAaIA·TION or IONIC STRENGTH •

IQEVEISlBILITY Ptot • • • •

• • • • • . . •· . . .

• • •

• •

. ·• . • • •

• • • • •

• • •

• • • • • • • • •

fOLA!OOMPHY or nm d ... TAJTRATE AND d•MANNITOL. 'tlLWitATE COMPLEXES •• • • • • • •

O'tHEl METffQJ)S AND SUGGESTION.$ FOR FU~ womc B IBX.IOOBAPHY • • • • • • • • • • • .• • I • • • •

iv

• •

. . "

• •

• • • •

. " .

• •

Page 1

4

8

• •

10

11

12

13

15

16

19

20

• •

• •

22

24

27

HlSTORlCAI. BACKGROUND

AND

GENERAL INTRODUCTION

l

2

In 1782 the element tellurium was di covered by

Baron Frans Joseph MUller von leiehenete1n. Miiller first

isolated the element fr.om fiansylvanian gold ore (2).

Klap)tloth verified this work and in 1798 proposed that the

substance be called tellurium. The etymology of the word

begins with the Latin now:1 tellus, m an1ng arth.

Students of ltoman mythol<>gy will recall t':te ancient deity,

Tellus. goddess of marriage and fertility. The history of

tbe discovery of tellurium is a. pa:rttcularly inters ting

one. Serious students of th~ element will enjoy reading

the ac.;count given by Kat:y Eliva Weeks (3,,4,5).

The propertie$ of tellurium are consistent with its

position in the periodic ·table as element number 52. The

elenltnts of Giroup VI include the non .. metale oxygen and

·sulphur, the semiconductors selenium and tellurium, nd

the radioactive metal polonium. Selenium and tellurium

are closely related in w.any ways and they are .often

discussed conjointly.

3

Xn aqueous solutions the most comm.on oxidation

States for tellurium are,•2, 4, and 6. In the plus six

state tbe element is u$ually encountered as telluric acid,

a6teo6• When the element or :lts oxide Te02 i& subjected

to sttong oxldlzing agents, tellurtc acid 1& formed.

The electronic configurati.on for the native element

(gl"J 4a105s2Sp 4 penn:lt& d2sp3 hybridid.tion foi- the h x­

ava.lent atom 4nd explains the diamagnetic octahedral con­

f1gui-ation of the ac1d11 te(OH)6• This octahedra.lly

syrmnetrioal structut<! was experimentally confirmed by

Pa.ultng (6).

Te1luric acid is a weak dibasic acid• the first and

sec;ond ionization constants being reported as 2.00 X 10·8 •12 and 9. 2 X 10 respe.etively (7). lt ia a fairly strong

Oltidi~in.g a.gent and tends to polymerize ln solution. A

three-di.Jneneional network may be formed by hydrogen bond­

ing. An important oonsid~ration is that telluric acid is

not analogoue to the other nexa.valent group stx acids.

namely• sulphuric (H2so4) and eelenic (H2seo4) acids. The later two, unlike tellur1c a.cid. contain nonhydroxylic:

oxygen atoms and are thus much stronger acids.

4

POLYOL COMPL!XES

That polyhydroxy alcohols and ox-yan:l.ons form compl x

ions ha.a been established for some yeQrs. Complcxa.tion of

this sort has been observed since at least as early a.a 1842

when Riot (8) noted thtt,t sugars enhanced the acidity of

boric acid solutions. Thi$ cha.ractet:i&tic of enh need acid­

ity is clue t,o the faet that the complexation effectively

pulls the anions out of the ionization reacticm, thus forcing

lllOre of th~ neutral acid to dissociate. In addition to

boTic acid,, polyol complexes h&ve been studied fo:r: phenyl ..

boric, germ.ante, arsenious, periodio, and tellurie acid.

The most important work :Ln this area ha been don y

J.O. Edwards at BrO"wn University and P.J. Antikainen at th

University of Helsinki. Edwar<ls ss !! have published a

number of papers in which polyol•tellurate complexes hav

been considered (9.l0,11112,13,14,15,16). Potentionietric,

pH, and spectrophotometric methods wei:e employed. Anti•

katnen (17) has used potentioroetric nd cryoscopic pro•

cedures for similar studies.

Edwards has proposed the following general equation

for sitll.J)le glycol-orthotellurate complexation:

..

s

(I)

OH HO· I OH .\I _/\w

oa

HO 'c1m

+ 1 CHR.

ml

OH HO I 0 \ / 'cua

-~> Te I / \/caa

·O o OH

+ 2HOH (II)

the foi:mation constant• weJ;"e found to be Larg aQd only 1:1

comple~s were considered extant. The driving force of the

reaction is an entropy increase related to the formation of

3 products from 2 reactants (13). A five membered ring is

favored by the 90 degree O•Te•O bond angle.

In later woi:l¢ IAnese (18) proposed a sit.nilar structur

fqr the d•tartrate•orthotellurate complex.

'\ /Q­ C l OH

H-C--0...._,__ I .......... oa I Te ..

H-C--0/ I 'O ... ~ ON I\ 0 Q ...

A thorough polarimetric study of this complex gave evidence

foi: a one•to•one stoichio1netry. Apparent stability

conatanta were found to be 45 't 2.5 at pH 9.5 and 62.0 't 3.1

at pH 12. An unalysii of the lithium &alto..:: the complex

6

ind.teated that the charge on the species was •3. That the

carbonyl group$ are not susceptible sites w $ shO\.m by the

la.cl< of variation in pH for complexation io unbuffered

solution. the inf't'a~ed spectrum of the earboxyl group was

not affected by comple:st formation, thus p~ovidiug additional

evidence.

The tartrate complexation require$ the removal of

hyd~oge.rui front the hyd3:os.y1 groups. This should expl.a.in why

the stability constants var; with pH (19). In addition, the

relative participation of the species H0Teo6, n5Teo6-, and

H4Teo6~ in a pff dependent w4y must be considered. It ie

underetand.ible that the probability fo~ the complex to form

1,fhould decrease r.apidly below a certain pn and become neg·

11gible in strongly acid solutions. Lanese givee lower

limit of pH 5 and concludes that the fot"tn4tion of the complex

is dependent upon the existence of the tartrate ion c4n4°62

a:t~d independent of the o:tthotellurate apecies that may be

present (20).

The fact that selenium (VI) and eertain other oxyanion$

do not complex with tartrate would suggest a valuable

ana.1ytical application. Lanese developed a polarimetrio

method based on the direct dependence of optiC4l rotation on

the additicm of tellurate to solutions of d-tartrate (21).

7

tt has been i.ntima.ted (22) thae the complex might be use­

fully employed in an ion ~xchange separation of tellurate

from similar oxyanions. Adsorption chromatography on an

alumina column ts another possibility deeerving con&idera•

tion.

Tellurium ts most popularly detetmined gr•v:lm tri~

eally by reduction with sulphur dioxide in a hydrochloric

acid mediWD and may be sepa.l'ated from selenium by distill·

atton from a solution of mixed actds (23). Sulphur dioxide,

however, will only ~educe Te(IV) whereas hydtazine will

reduce both the IV and Vl oxidation states (24).

A mare typical polyol•tellurate complex is that

focned by the neutral ligand d ... mannitol. Studies of this

complex by Edwards (9-10~ 11, 12, 14, 15) and Lanese (25) indi·

cate that a one•to•one oomplex is formed. These lnvesti•

gators.have not considered that higher order complexes may

be poss:tble. Since each mannitol moleeule contains six

hydt:'oxyl g'X'Qupe tt is conceivable that three tellut:ate oxy•

anions could react with each ligand. A pH and conducto•

ltletr1c study by Gate and B.ichardson (26) revealed the exist•

ence of a 2Ma.n.:3te complex after a 10 day equilibration

period. Presumably this •pecies would exhibit the following

structul"e:

a

The pre.sent investigation was undel'taken with the

intention of contributing additional evidence to the

e1uoidation of polyol•tellurate comp1eKe$. A .wide variety

of methods are available .for studying complex: ions and the

recent inonograph by B.ossottt and Rossotti (27) pt'ovide• an

GJ:&:tettalve a\11JllD4ry. 'Being inclined toward electrochemiatry,

a polarographic etudy -was initiated. the use of polaro•

araphy in complex ion studies ha• been reviewed by crow and

Westwood (28).

POJ:AB.OGRAP8Y

Tellur:tde, tellurite. and tel1urate are known to he

po1ai-ographf.oa11y active. The polarography of tellurium (VI)

has been established for some years. Nevertheless, there ia

a certain lack of theoretical study, and where sueh studies

9

have been reported (29,30,31) theJ:e remains tnUch room for

further work and a necessity for correlating the result of

eai-11er investigators.

Tellurtum (Vt) exhibits a well-defined~ though

irreversible., pola.rogra.phf.c wave. In a coul.ometric investi­

gation Norton !! !! (29) were able to shatt that the wave

represents an eight electl:'on reduction to the .. 2 oxidation

state. It was noted that media. containing complexing agent

such as tartrate, <:titrate., and ammonia improved the defini­

tion of the c~thodic waves. They did not establish whether

thi$ was a result of the fot'm&tion of complexes with

tell'Urium (Vl) or a reduction product. Lane e (30) studied

the anodte tellurium (VI) wave and discovered. that tartrate

d1stol:'tS Ol:' eliminates it depending on the c:oncentration.

POLAB.OORAPHlC 1NVES'rtGAT10N OF TELLURIUM (VI)

AND

POLYOL-OB.'rROTELt..tmATES

10

11

APPARATUS AND MATERIALS

All pola.r:ographic m-.sur•mients were made wi.th a

Sat;gent Model XXl r:ecordlng polarograph. A Leeds and

Noi-ttn:up Type. K•l potentl.ometer (with an t&N 2435•C

reflecting galvanomete-, tmd Weaton Standard Cell) was uaed

co obtain accurate e .• m. f. values. For pK measui:-ementa a

Leede and Northt'Up Model 7405 expanded sea.le pH meter s

employed. All ebemica1s were reagent grade with the

exceptiotl of metatelluric acid W'htcb waa obtained CP from

the Amend Drug and Chemical Company, Inc.

A standard, non•thermostated, ff ... cell was u ed with a

potassium chloride agar bridge and Saturated Calomel

Electrode. A Fisher capillary under a 40 om. mercU'ey bead

was used for all eJ£periments. Sol1.1tione were deaerat d with

~ter•saturatec:I nitt:ogEn.t for 1.5 minutes befoite each expert•

ment. · Th$ S.C.E .• was periodically checked with a Zinc (11)

stand&rtl in lM potassiUll\ nitrate.. The half-wave potential

11 reported to be •l. 012 volts vs. s.c.E. (.29.32).. The

s.c.E .. "went bad" sevel'a1 times during the course of this

wo1'k and had to be renewed. A significant improvement in

stability was noted when an H•cell \rith a larger diameter

referenc cOUlpartment wae obtained.

Before any ine ningful inve&tigatiou of the complex

12

could be undertaken it w. s necessary for tt•is investigator

to becom~ fam:l.1:1.ar with the pol~J.rography of tellurium {VI).

The disadvantages of limited time and education made this

preliminary work more lengthy than originally expected.

An irreversible wave of this SO'C't affords numerous ;Lnter­

est1ng1 but time consumin~h problems.

MEDIA

lt wa.a first thought that the Britton-Robinson uni­

versal buffer might be used to advantage at varying pH' ,

The buffer is compoaed of a mi~ture of phosphoric, acetic,

and boric acid• neut~alized with sodium hydroxide. It w s

prepat'ed according to th~ directions ·Of M'ftller (33). un­

fottunately. in this medium* the limiting current of the

tellui:ium (VI) wa\te was not sufficie11tty separated from the

termination of the residual current) where hydrogen ions

are reduced.

Thia l)roblem waa extapt at pH's as high as 10. At

low pH's no cathodic wave could be distinguished. Thia

re.chest unwieldy buffer we.a discarded in favor of a cat'·

bonate•bicarbOnate system.

Previous investigators have ~.o-;;.i'>trated the useful­

' ness of such buffers for studying the polarography of

tellurium (VI) and polyol ... tellurat:a cauplexes (25,29). A

pH of 9. 65 was chosen for the initial wo~k. The ~a.t: odic

wave ia suitably defined at this pH. In addition., Lane e

showed by a polarim.etric investigat:tot1 t'1at the d•tartrate•

orthotellurdtc complex exists most conclusively at pH's

abova 8 (21).

The ionic stl:'ength of the carbonate•biearbonat buffer

wa1 nbeefed up" with potassium nitrate. A supporting

eleet:tolyte of relatively high ionic Stt' ngth • relative to

tellurates pe:r£nits the assumption of concentration inde-

pendent ac.tivity coefficients and a negligible ¢el1

resistance.

CONCEN'XBATtON STUDY

The relationship of the diffusion cut.'X'ent to concen•

tr4tion was found to be linear over a range of concentra•

tion~ from 1X10""5 to l X 10·2 Molar metatellurio acid.

The ieC ratio under the aforementioned conditions liil8 32. l

anilliamps ... 11ter•mole "'1 O'ig. I). The ·diffusion currents

1!1ere measured at 1.5 volts vs. s.c.E., with o drop time!

of 2.7 $econd8, and a mercury flow rate!!! of 4.1 mg./sec.

The diffusion current cQnstant, 1 = id;em213t1/6 1 is

calculated to be 9.9 (34).

DIFFUSION

CURRENT

14

) ..

60

'"' (JJOmps) 5 0

I

40

20

10

0 2 6 8 . 10 t~ ... 1-~' ·. 4

{ H Te 0 ) ·- ·- M x I 0 2 4

'18

Fig. I.

The depen~ence of the diffusion current on the

molar concentration of tellurate in a carbonate-

bicarbonate buffer, pH 9.7

15

At tellurate concentrattons above appro:gimately

S X 10·4 a very substant~l maximum developed. Triton

X•lOO was found to be a suitable maximum suppressor.

At concentrations near .Ol M streaming became

visibly evident in the electrolyte and a black pYec1pitate

formed around the drop. Eventually the entti-e solution

contained a suspended black solid. It is suspected.

though not demonstrated, ti1at the black substance is th

free element (31). Telluride will reduce te11urate

aecoTding to equation (III).

(III)

The apparent diffusion control of the wave height would

ind:Loate that this proceas occurs outside of the diffusion

layer.

The anodic wave l:caehes a saturation current in•

dicative of an electrQde reaction limited by surface

phenomena (30). A black precipitate 1;°ol!'med by this reaction

has been shown to be mercurous orthotellurate. Hg2H4Teo6•

VARIATIOM OF THE MERCURY HEAD

The rate of xnercury flow th:tough a dropping mercury

·electrode ts proportional to th~ pressure head above the

16

capillary tip. A slight variation is caused by an inter·

facial back pressure which has been neglected in the present

woy;k. The llkovic equation for a dlffu$ion ... controlled

polat.:"ographie wave (IV). with all other things being equa.1.

reduces to (V), where k is a constant and !! 1$ the mercury

head in cm.

i = 607nI>112eni213t1/6 d

id - khl/2

(IV)

(V)

The observance of thia proportionality i often used as a

cr.ite~ion for diffusion control. 'fhat the tellurate wave

behaves in thia tnanner is shown in Pig. II by the linear 1/2 ' plot of id vs. h • If the wave was QOntrolled by a

chemical reaction in the di.ffusion layet' (i.e., a kinetic

wave) the wave height would be independent of h. For an - adsorption controlled wave the wave height. is proportional

to h. - EtECTR.OCAPlLtARY DATA

Electx-ocapillary data t1ere obtained for 1 X 10·4 M - metatelluric aei.d to a carbonate-bicarbonate buffer of

pH 9.7 (Fig. Ill), and for the suppotttfng electrolyte alone.

The time for 25 drops was measured versus the potential every

DIFFUSION

CURBENT

().lamps}

17

22

20

16

14

t2

3'0 40 50 h (cm.)

·so· Fig. Ila.

22

20

18

16

14

12

5 6 7 8 ;· hl/2

Fig. !lb. /

The dependence of the diffusion current on the

mercury head and the square root of the mercury,

head. 5 X 10-4~ tellurate in carbonate buffer,

pH 9.6

I

/

-c-c.,

18

0 s

U') C\J • -

It) ~. w (j (])··

V)

o> I() w

• I

IC) (\I

•

• H H H

0 I()

0

Cl)

•

(/) Ul C\I 0

eo

Q.. . .,,,.... 0

•r-l

:E « 0 u I'-' (D ~

~ a:: Cl ._ 0 "' ·-

19

.OS volte f~om Oto 1.8 volte vs. s.c.E. The two hyperbolic

curves were found to be almost identioal1 both reaching a

magimum at .52 volts vs. s.c.E. This apparently J:egular behavior is in contrast; to

that of the anodic t~llurium (VI) wave (30) and the cathodic

telluriutn (IV) wave (31). Both of these exhibit irregulal'~

1tie$ in their eleetrocapillary cu..:ves indicative of

adsotptton 0n the drop surface.

Although it ie certain that the reduction involves

eight electrons (29,31) the nature of the lectrode proces•

for the cathodic wave has eluded sati$faetoey explan tion.

VAl.lATION OF IONIC Sft!NGTH

'fhe effect of increasing the ionic strength was .. 4

studied with 5 X 10 M metatelluric acid in a carbonate• - bicarbonate buffer of pH 9.65 with an ionic strength of

0.21... Potassium nt·rate waa added in five ter>s brin ng

1 ft'OP\ o. 21 to 1. 81. - At the initial ionic etrengt:h of 0.21 the -wave ex­

hibited a very pronounced maximurn followed by an erratic

limiting autrent. 't'he ma.xicum completely disappeared when

I was ~~ncreased to 0 .. 46,. OveJ; the set"ies of six experiments .....

the s1npe of t'he limiting current increased, becoming less

20

distinguishable frorn the hydrogen limit. This makes the

accurate m.ea.suremen·t of E~./2 difficult at high ionic

strengths. The half ... wave potential moved posittvely ft:"om

.. 1.36 to -1.30. The hydrogen background curve also moved

positively.

This behavior indicates the necee.sity of ca~eful

ionic strength control when the cathodic: wave is used to

study a te11urate complex.

IlUtEVElSIBILITY PLOT

A reversible potarographic wave may be described by

equation (VI).

(VI)

The slope of a plot of •E ve. log (i/id •i) will give a

value of ,e consistent with the number of electrons involv d

in the polarograph1c i-eduction. Iri:eversibility plots for

tellurate and polyol•tellurate comple•es (Fig. lV) give

values fo~ !! in the netghbo:ehood of • OS. This indicates

that the cathodic tellurate wave is an extremely irrever•

stble one since it is known to involve 8 electrons.

21

j I

. I

l.!5

I •

1.50

-E vs. S.C.E.

1.40

1.30

l

1.25

.. I 0

Loo i / c~ - i> _ I Fd.g , IV. Irre'Versibility Plot for 2 X 10-4li tellurate and

· ~ X l0-3!1 mannitol in carbonate buffer, pH 10.5.

22

POLl\ROGRAPRY OF THE d ... TARTRATE AND d·MANNITOL

TELWRATE COMPLEXES

the variation of th~ tellurate half--wave potential

wa$ investigated as a function of ligand concentration for

the d•tartrate and d-ms.nnitol complexes. Fors. reversible

eyst.em it is possible to both detei:mine the sto1chiometry

and S·tability of a polarographically active complex. The

nece11Jsary relationships .are, derived fr·otn the Nern t qua•

ti.on and the Ilkovie equat:i.on (35 ). The stoichioruetry is

dete17mined according to equation (VII). where p is the

number of ligands pel:' central group and C is the molar

concentration of lig4nd in the electrolyte.

(VII)

Polarography ts cel'tainly not a. good method for

studying tellurate complex.es because of the extreme

irrever.sibility. Aside £i-om the irreversibility of ·th

wa'7e, the acidity of the ta~trate ligand defies: the pur­

pos.es of the carbonate-bicarbonate buffer. The buff r

capacity is not capable of handling the high concentration

of tat'tl!'ate used here, however, constancy of pH is essential.

lt ws necessary to ad.d • 2N NaOH to push the pH back to the

23

original 9.65• The ionic strength was thus maintained at

about 0.2.

A series of experiments wette run for both complexes

and the resulting data were sporadic. inconsistent, and in•

~onsequential. It was not:i.ced, however, that the data

¢Ol1ected for the inannito1 comples was time dependent

whereat the d•tartrate gave time independent results. Th:t.a

ts illustrative of the very slow equilibration of mannitol•

tellurate found by Gate and Richardson (26).

There are a m.m.ber. of vays in which irreversible

;polarography can be adopted: to compl• ton studies (28).

One empirical method that can be applied to atmilar itua•

tions is to substitute en 9!! term fott !!• The en term is

the value of ttnu det:ermiruad from an irreversibility plot.

tn the present work gn ts, of the order of .os and the empirical p~edure does not improve the applicability of

the AE112 data. In.-eversibility being a matte:t of degree;

it le suggested that the !!!'! u fudge factor' is useful only

for mueh le•e irreversible situations.

OTHER METHODS

AND

SUGGESTIONS roa FU'l'UllE WORK.

24

25

Since the polarographtc investigation provided little

evidence with regard to complexation,, and since time was

short. it was decided to pursue the n:tattel,' of the time

dependence. of the mann1tol ·Species with already proven

method& .•

A spectrophotmnetri~ tnvestlga.tion using the logarithm

t:"atio method (36) ~ s very auceesefully used to atudy the

mannito1 complex foaned i.mxnediately after mbd.ng the ligand

and metal (i.e •• ~ one,..to..,.one c0tnplex). An attempt was

made to duplicate the wo.:k of Lanese (25) and then follow

the compleJ(&tion ve~sue time~ Eape~iment were performed

using both the Perkin-El.met' 202 and the B$Ckman DU ulti-a•

vtolet spect:tophotometers. These instruments are apparently

incapable of the aensitivlty e.f the mot-e eophistioated Cary

Model XI used by Lanese. No workable data could be

obtain'ed. Tb:ls is one of the most applicable of the possible

methods and it should be considered in the future.

Gate and Rich4·tdson (26) used the continuous 'Variation

method to investigate the d•mannitol and erytht:itol complexes.

Va~iation of pH and conc:luct1vity showed that the 3Te:2Man.

complex is predominant afte~ about 10 days equil.ibrs.tioo"

their data fot:' lD/innitol was duplicated (with less sensitive

26

equipment) and the re&ults confirmed.

A pH meter of sufficient stability and sensitivity

was not available to permit the initiation of a. pH study

according to the procedures of Edwards (10).

l. Becher, J.,J., 11Aeta Laboratorii Chymica Mona.acnsi, seu Phys ica Subterranea," ( 1669) ; Howe, H. E. • "Chemistry in Induatry1t1 3rd ed,.; Vol. l, The Chemical Foundation, lnc:, (New Yoi:k1 1926); Weeks, Mary Elvb:·a, 0Discovery of the Elements,0 Journu .2£ Chgm!cal Education (Ea•ton, 1956), .p. 302.

2. ~ller, F.J. "Versuch mit dem in der Grube Mar;lahilf in dem Gebirge Facebaj bet Z.alatna vorkommenden vermeinten gediege~et1 Spiessgla l<onig,*' Physikalische Arbeiten der ei.ntra.chtigen Freunde in Wien l (1), 63-.9 (l783); l (2), 49-.53 (1784); ! (3), 34:52 (178S)~ thxough Weeks, Mary Elviioa11 °Discoveey of the Element •0 J,ournal !! ~l1em.i~!! Education (Easton, 1956), p. 336.

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