CII!PDI U

\ Thirtem .w .. arylb141'0SU'to acid• han been txam1Decl "'~·~·

aa reagents for graVimetric eeUaa\1e or cobal.\ and copper.

N-m-ChJ.oropbenyJ..p•methox;r be&UI ... bldJ'«nah acld which vaa

round to be the most w1 table reqea'll. 1n Vle eeriea 11

proposed for the separat.ton of cobalt an4 eepper and their .. ,

gravimetric determ1naUon ia preMDce of eaoh other.! . ...-. Cobalt can also be veighe« a1 wlphate after treatmeft\ ot

preci.pl tate w1 th INlphuric acld and n1tr.\c ac14. ( The '··

metals are precipitated separat,eq vitob We reaseat £..-'·

their hot but'.t'end 1110lut.ton. \ Cobal' ad eepper an preo1p1• __.

tated at pH 5·5 ... 6.5 and 3.S • a.,o reJPect:tvelJ and ve1S)le4 .o

aa such after 41'y1ng at 110 c. !he aetal cet~~Splex eoneJPGD4

to the formula co<c1lt.u11No3cl)2tad eu<c1a.u11No3cl)2• B7

adjusting the pH or 1ihe 80luUCID& it :la poaatble to tepa-:rate

cobalt and copper from each other and to eatimate them 1n

presence of several foreign 1•••

N-PhC!ft7lberulct:Q-drozaldo acl4, PBHA, baa been

recommended as a grav1metl'1o reaget. tor aevenl •tal

1ona < 1·3>· Cobalt and copper bll'H baea cl'llY1Mt.J'1ta11J'

estimated uains PBliA (lf.) 1a prennoa ot aactb other. ID

the present investigation, Wneen nev li•&l7l•b,'rdn:um1o

acids w1 th similar functional II'OUP1rll aa PBHA hue been

examined tor their possible uae aa a reqent tor sranaatl'io

detel'lll:111at1m of cobalt and coppu. or \be new li·&J'¥1-

hydroxam:le acids examined N••Obl.OJOPhiiDJ'l-p-aetboqbea.IO-o.

hydroxamtc acid, tr1v1}l1atau4 u ...... CPMBBAt baa been fO\IDd

to be the lllOst suitable rea,g«~~t. tor aepant1ca and de\end.•

nation o·r cobalt ead copper. the pre~itate Gbte1ne4 1a

granular, nOll aticll;y, stable ead ea.al;r t:Uilflnble. Illle

to tbeae propertiea ead the hip me.l.ecul.ar we.tcht. or \he

complu,and low conversion taot.ora, i.e. 61!.33 tor c.-alt.

complex, eooversion factor 0.09618, 616.tit- tor eepper OGIIplu:t

convertd.Cil factor 0.1030. the reacent 11 well suited tor

gravimetric estimaUon ot th.e ebo're W. metala.

AQparataaa& . 'I'be pH aeasuremcta were aacle bJ' a Srat.n~Uca

ponu~e pB uter fype 323• BDB wide all4 nai'J'Olf J'IID&8

1nd1cawr papera were emple,red. tor rapicl pH detel'lll1nat10Da.

Corning b1'81lc1 a:Lntered alan oneDll or pei'Odt\J G3 ·vu

uaed tor filterauon.

RtgMtaa

methOde described earlier 1n (Chapter II). Aa the bJdi'UUiio

acids are only ve17 alightlJ Ml.Uble 1ra vaMI' a o.01M

aolut.t.cms in alcohol were uat4 1n which t.b87 &J'e tntl;r

aolub~e.

,;;olut;;tgp of metfll .1.'111' Separate atandard IIOJ.ut.t.ona of

cobal.t and copper were prepared trom A.a. grade cobalt

nitrate and copper sulphate respeottveJ.yln gl.aaa dist.t.lled

water. Each ml or the aoluUOil Ollllltdaad about 6 q ot tho

metal.. The cobalt end copper ecata\ ot \he Hluticm wu

detel'lll1ned by EDtA methode

Solution of diveree 101la watt prepared by tbe

method of West (~) using A.B. -.bem1cala.

A mown qUanti v of eobalt or copper

soluU.on was diluted to 2SO Ill with disti~led water and

heated to about 80° on a water bAth. (In case ot cobal\1

10 m1 or 2% hydroxylamine hJdi'OCblol'ide were added w prevent caxidat.1on or Co(II) to Co(Ill)). o.o1M aolut.ice

ot N•a1'1l.bTdJ'oxamic acids 1n al.ooho1 wu alowl7 ~ded to

the hot solution or the metal with CCibstant at!n11lg.

A 10% aolution or eodium acetate was added to ma1nta1rt

the pH between ~.5 to 6.S vhtle eat.t.matlng cobalt.. Fer

eau.&t.lfm or copper pH vu adJuated to 3.5' t.o ~t-.o by addin&

1N aulphuzo:l.c acid and 1~ 1041• aoeate. A INmlhl'

prec1.p1tate vu obtai.ned ill eaeb oue. 1M ld.ztun vu

stirred ocoaa1onaJ.l7 dur1q •• beur on a MiH•g wahl'

bath. The precipitate Val t1l.tered Sa a 8ilatencl ilUI

cruo.tble ot porouv G-3, vubed vUh JaR water and

t1na.J..4r with 20% aqueoue etbeael. fbe o~~~plue• wen

dzo:l.ed at 1~0° and we1ibe4 d11'eot.:q u (C1~e-u, 1ao3Cl>2Co or eu.

Cobalt can be cGOYel'te4 and veiibed •• sulphate

by heating with sulphuric uul n1.t1'1o aoid.

On examination the u ...... CP)(.BBA vaa found to be

the beat reagent tor graYilaet.J'io d.eteJ'Id.DaUQ'l ot cobalt

and copper. benet it was atudied 1D detaU.. WhUe eaU•

mating cobalt and copper tocetu:r., copper wu eat.tmated

first and then cobalt waa eatlllatetl after add:l.U• ot

b;rdl'OJqlamine b;ydl'OChlor14e.

Granmet.W •nva1;1on o( PM\ 0'• '!illfUI' v"ns

H·m-CfMBHAa A ai.dure containin& known UOUDt ot

copper and cobalt vaa diluted w 2;0 ml vi\b disUlllcl

water. 1H aulphur1c acid and 10% aod1Uil aoeta.te aoluti•

were tben added to ad.1utt pli to about 3•8• fbe aolutiGD

was heated to about 80° and copper vas precipitated bJ \be

gradual addiUOD or o.o'IM aolutica or I..,.CPMBBA ill ethanol.

The copper precipitate waa heated • the water bath tor

•e hour with oocaaicmal 1UI'I'1rlg and tilterecl • a

G.) s1ntered glaaa cruc1l)le1 wubed weU with hot water

and. t1nally w1 th 2o:"' aqueoua ethanol. '1'be p:rec1p1 tate

was dried at 110° to conatant vetabt. !be coppezo oontent

of the precipitate was caloulated ullq the tactor Oe103•

Xhe .filterate and we.shinia were enporated to abOUt 300 Ill

and .filtered if necessaey. Betore the nb .. quent deter­

mUI.atian of cobalt 10 m1 of 2$ lVdJ'o,Q'la•tn• byclroohlol'1de

we.srdded. Cobalt was then dlterained aa deaCJ"ibed ~·

It the cobalt is precipitated without pr.l.or adc1U1CI'l of

eyd:roxy-lemine eyd:rochloride the results obtained. ate

slightl,y h:l.gh probably due to the tol'll!atl.on of 1111all

amounts of cobaltic complex in the precipUate.

RESUL~S Ali}) DISCUSSIQ!

!rbe experimental reiUlte on the quanUtaU:re

determination or cobalt(II) and capper(II) are glvtA 1n

Table a

acids. The experimental rew1t.e e the quan·t1tat1ve

determination of cobalt and copper ue liven in tables 3

and ~ respecttveq. fhe re8'11lt• on the effect of cU.nne

ions ua sraYimetr.l.o eati.mat.t.GA of CObaU an<1 copper ue

given 1n :Cable s. The renlta • eeparat1on of cobalt

and copper are shown 1n fable 6.

ifted of Ftnigp sea 1'he ettect of various 1GDs were

studied 1n sra't'illetZ'J.c detel'lllinat1Clll of cobalt and copper.

Wif 1

GMV IMEWC DIS7DI'AJ',JM 9l G9JWE

--------------------------·············- ............... ·····----s.No, l!yd:roxamic ac14 Compout.t.•

---·----------·--------------·---·--··············-·········------1. H-o-Chloropbenyl• < c13~No2c1)2eo ~,2.28 219 ~ ... ~, Slt.10

benao-2. M-m-Chlorophenyl- (c13~N02C1)2Co na.zs 22 .. 100.)0 1oo.aa.

ben so-). N-o-Chlorophenyl- < c14H11Bo2cl)2eo ~ao.33 219 ~.,1 !$3.90

p-toluic-, 4. N-m-Cbloropbenyl- <c14H11H02cl>2eo ,-so,.u 22J ;4.)0 ,...as

P•toluic-t , ,. N-m-To.l7l•P•Htboq(C1;S, .. HOJ)zCo 5'11.~ 214 S0.20 a.,.6ft. ben so-•

6. N-o-Chlorophenyl-p•(C14S,1NOlCl)zCo 612.33 203 SJt,,, Slt·09 methQXT·benao .. ,

1. N-m-Chlo:ropbtnfl•P•<c14a11xo3Cl>2eo 612.33 210 32.10 32., ... methOJQ'•beruto-,

a. N-o-Chlo:ropb.enyl <c, .. s,,•ozCl)aCo seo.)) .201 32.10 32 • ..., phenyl aceto-,

9· N-m•CblOI'Qpheny1 <c1,a111«)2c1>2eo 60'..3J 21t6 ~.,., Slt.19 cwm.amo-.

10. r~-m..Chlorophenyl-p•( c17a1fo2cl) 2eo 661+.1.? 221 5'0.19 ;o.a.o ter.but¥1 benao-1

11. N-o·tol7l•P•ter. (C18~0N02!)200 623.63 186 ~.,, Sit. Oft. bu-1 benao-,

12. .lll-m-tol¥l•p•ter. butyl benao-,

(C1B~li02)2Co 62).63 210 .32.6~ .31.89

13, .N-p-toJ.71-P-ter. < 91e ~ol02 >a eo 623.63 220 , ... S1 ~.08 butyl benao-,

_______________________ ....._ ......... 11 ................................... ....

TAJilLI 2

·------.. ---------------------------------········· 14 ··········-----

s.No. Hydroxamic aci.d Compollit.t•

·-----.--------·--------------------········----------- ··--------1. N-o-Chlorophenyl (C1 j~ll02Cl) 2cu ,~.19 193 32.~ 32·09

ben so-2. N-m-~1tlorophenyl- < c13~No2cl>2eu '"·" 201

32oSlt 32.oa.. benao-

3. N-m-Chlorophenyl-p-tolulic-

<c1~H11No2Cl>2cu ;~~ aolt ;1.00 ;o.1o

1+. N-m-tolYl-p-metbQlY(C1;B1..,No3>2eu S16o10 200 )2.60 32.;o benao-

;. N-o-Chl.oropbenyl-p-<c1..,~ 1xo3cl>2cu 616.~ ao; 32.60 32·10 metnaxy benzo-,

&. N-m-~bloropbenyl·p-(c1..,B4 1Bo3cl)2CU 616.9 ... 206 S1.~0 ;1.10 methoxy benao-.,. N-o-Chl.orophenyl <c1 ... B41No2CJ.>2eu ;814..~ 1a; 32.;o 32.~0 ph&n11 aceta-

B. N-m-Chl.oropbenyl (C1;H,1H02Cl>2eu 606.96 219 32.60 32·~0 cSnnamo-1

9. 1'1-m-Chl.oropbenyl- ( c17H1.,so2CJ.>2eu 669.08 209 32·~ 32o11t p-ter.butyl-benao-

10. N-o-tolyl-p•te:r. < 01e ~aK0a> aCu 628.2lt 222 32.Slt )2.Q6 butyl ben•o-1

11. N-m-ToJ¥l•P·••~"• (C18~0N02)2Cu 628.2 ... 191t 32.;a 32.C8 butyl benao-

12. N-p-Tol.yl-p•te:r. <c,aa.zoN°a>aCla 621h2lt 201 32.~ 32.36 butyl benao-

13o N-l-Nap~l•P• {c1aE11t•oa>aCla 616.1'+- 223 )l.;o 31.80 me-l benao-

-----------------------·-··················· ·-·------------·-··--

WLICl

GMV IMlm\IC Dl!lTUQAtiQI oz MAALt WUH

-------------------------···~~--------···---------------------Weight ot Co taken mg.

Weight of tbe ccmplex <1111>

------------------------------------------------------------24.8 27'7.5'0 24.18 -0.02

~., 307.5'0 29.5'4 +0.04

33.4 3lt8.o5' 33.43 +0.03

37.9 393.95' 37.86 -o.04.

40.2 '+18.20 40.25' +0.05'

-------------------------··--------·------------~---------~

GJ!AVIME'WC l?ET.!!DA!l@ 91 C9frp Will

------------------------·--···---·-·····--------...--·-···· We1ght·Of \be complex <•s>

-----·-----·-·----..------------·-·····---------·········-··--20.!1 196.95 20.lt8 -0.02

22.6 221.95' 22,61 +0.01

2'5.7 21+9.91t- 25.70 .. 28.2 273.!$0 28.17 .. o.o.3 31.1t- 30So9S 31.4S +0o05

............. -------·--------....................................... ..

WLJ 5

lfFijCT Ql !QB§!GJ IQIS II QNmmrc gmazp Ql

-----------------------·-----------······-------·····-------Added Co taken c. fNld Ca taken <..'u toun4 lon 1111 in II& uac 111111 ill Jill

-----------------------------------······---······----------Pb+.2 100 25.20 25.08 31.lt7 31.o&f.

Hg+2 100 25.20 25'.30 31·"'' 31.08

Cd+.2 100 25.20 24.91 31.47 30.82

Zn+2 100 2$.20 25'.0, 31.-..7 31.06

Mn+2 100 25'·20 as.os 31.&t-7 30.06

Ni+2 100 ... • 31.lt7 31.83

As+3 100 2$.20 zs.o2 31.lt-7 31.06

u+6 100 25.20 as.oo 31.-..7 30.82

PO •3 4 100 2$.20 25'·09 31.lt7 30.21

___ ...._ ....... ...,......._ .........................................................

tABJ.I 6

-----------·-----------------------------------------------· Metal taken <me>

Cu co

-------------·----------------··················-------..---

so.18 so.a.a

---------·-·----------···p ................................... ....

Pb+2, ua•a, Cd+2, za+a, MD+a, ut', u•l

and PO'+ •3.

N1+2 interferes in the dete:rm1Dat:l.• ot oobaU

but does not interfere 1n the detc'ldnat:l.• of copper.

Propettit• and CompgaUi!ll pt 1lbe pnglpU•M• The

cobaJ.t complex b pink gran\tlu and non at:l.oq vi~ the

composition (c1'+a.1No3cl)2Co. It 1a aoluble 1a alcohol,

acetone, chlorofoJ:m and ben•••· n 11 ~ensal.l7 stable

and melts at 210° •

The eopper complex 1a sreea g:ranulas- and naa

sticky wi.th the composition (c1.._s.11No3Cl.>2eu. It 1a

soluble in alcohol, acetone, ebl.orotom and buuine.

lt 1s thermalJy stable end malta at 206° •

The reae1::l.ons of the M·al'Jl b;rlboxuic ac1da w1 Ul

metal i.ona can aeileral.l¥ be :repreatDte4 aa u4ert

n'- .N-OH a•- N-O

"' tf1+ + n • +

R- c-== 0 a-c=o ~ n

n 1a aeea that five membeNCI ilmer complex ec~~pounda are

tonsed w1 tb tbe release of b7dJ'Oseo itlh

Jl}l+

The m.p. and cGDpOaiU.an of \be GC~~~Pluel vUb

N-a:ryJ.h7d:roxaaic acid• are c1v• 1n TablA~ 1 and 2.

Ef'fect of pBz Tbe optimum 1'8Die ot pB tor precipitaUc

ot cobalt and copper was found to be S.S to 6.S and 3·S to

4.0 respectively.

Infrared apectraa The iu.tral."ed .,..va ot .... CPNBBA

taken in cc~ showed peaks at 3070, 1630 and 930 oa·1

due to stretching vibrat1cm ot o-u, c.o md li·O :reapectlvely.

After c0111plex fOJ'IIIation tbe peak due to O..H atretMJna

vibration disappears. In tbe CCIII!plu: tbe lVd:ro&en ic

is J.oat and the oxygen atoll of O&Jbca7l SJ'OUP 1a

coordinated with Co or cu.

The abaorpticm peak due to ~l (C.O),

stretching vibration in tM apeot.ft ot Co and Cu-X.....

CPMBHA eomplexes 1s located at 1;80 an4 1f?S ca•1

respectively due to boniU.ac of C&1'tMID.fl oqgen atom to

the metal <-CeO - M). the peak due to u .. o atret.cmhg

vibration increases in intenaiw and is located at

925 and 940 cm-1 in Co and Cu-li....,._CPM.a.HA CG~Dplexea

respectivel.J.

It 1a ni.dent tra the preced1na cU.acuaaica ~­

N-... chlo:ropheeyl-p•metbQXJ beDao!q'dnzald.e aoid. 11 a unftal

reagent ror the grs:YimetrJ.e cletel'lllinatioD of cobalt aD4

copper. Hence, it 1e thou&ht wortJl.whUe to .-,pare the

present reagent v1 th the other corrnnticaal si'&Y1Mt:r1o

re~~.gents recQIIIJileraded tor eobalt. and copper. %he det.alll

such as name of the reagent., we1&hiq ton, inwrterenoe,

converllion factors end retuecea are a1Ten in fable 7 and

8 respect1vel7 tor CObalt (6•10) 8Dd oepper ( 11·18).

the discussion of the otlber Utbod.a tor

cobalt (9) and copper ( 19•30) bas been deUve.rat.eJ.J avoided.

tor the 1ake of brenty and looktng to the nature of pnMDt.

work. At halll already bean at.at.ed \be reaoUoaa of the

})Jdroxamic aCid a w1 th cobal' aD4 copper were enmhtcl el;r

because the reagents wert &Vallable eui]J and lheu anal;(•

tical potantiall U.ea were bdn& at.uUecl aa &ftV111etr1c

reagents for tantalum and BiobJ:ua.

It mq be noted that the rocent H.oa-CPMBBA 1a

not cla1med to be the ben zea.aent. tor the &:ra'filleVie

eatimat1on of cobalt and copper, tholllh 1t .U COIIparabl.e

w1 th the other reCG~D~D~~Dded reacentt. Fwtber, 1t 1s

enctent that the reagent can be proti'tdl¥ uaecl tor the

srav11letl"io 4ewl'lllirlaUGD of CObalt and copper and their

separaU.GD rnm each otbe:r. Marq of the CHI e •tala

TABLE 7

FOrtMS OF Gc'i.AVDm:ra;rc DErEhMINATION 01' COBALT

-·----.----------------------------------------------------·*=--------- ----···--------------~ * Reagent \'./eighable f'orm piT Remarks !>fetal/ 1-:ef"erenct l·1etal complex !"actor

--------------------------------------------------------------------------------·· I u III IV v VI

- - - ... ·-·--------------------------------------------------------------------·----------· q-H1troso-j3-Napthol

Potass1u. nitrite

Antbl'81lillc acid or s0d1.Ulll antbnmn ate

Pbenylthiohydantoic acid

Mercuric chloride and ammonium thiocyanate

Cxide/sul.pbate/ metal

2K)Co(NC2)6.3/2H20

<c.,n6o,_N) 2eo

co2o3

co[Hg(SCN)lt 1

acidic medium

.. Neutral or weakl.y acidic medi.um

-Neutftl. medium

CU(II), r·ln(II) - 6 Cd(II), Pb(II) interfere

Pb(II) lntert'ere 0.1262 7

N1(II) and Zh(II)0.176o 6 interfere

Separated f'rom - 8 . Zn(II~, Mb(II) Mg(II

CU(II), Cd(II) 0.1191 6 l.n(II), N1(II) Vn(II), Hg(II) 1nterf'ere

TABLE 7 (CONTD.)

---------------------------------------------------------------------------------------- ·------· I II III IV v VI -------------·---------------------------------------·· --------------·----.---- ····- --Anrcm1U11 t.h1oc,nate [co(C;'t~:)~ (scr:)2 rleutral. CU(II), Cd(II), 0.1282 enct p71'1d1De medium Zn(II), Ni(II),

Hn(II) interfere

8-Q1Wlo11nol CoCC9fl6Ho2 )2 4·33-14.!) Zn(Il), Cu(II), Hi(II) 1nterfGre

0.1!)5'2

or(· Nit.roso~-NaJbtb!fla- (C1cfi7<2C)3CO - CU(II), ?li (II) 0.1030 me and J3~nit.roso~ interfere c(-naph~]amtne

li .. -cblloropbefl71·P-•~enzo-h)'drC'DJI1C acid

(C14n11N03Cl)2Co !).!)-6.5 Ni(II) interfere 0.0962

-------·· ···-----· ··---------------------------------------------- ·--· . ·-···-• Other methods (MI\.)~ (9); KaCa~ (9).

6

9

10

-

N c:n ~

TABLB 8

FORMS OF GRAVIM!mi.!C DErii!hMINATIC.N OF COPPBH

------------------------·-------------------------------------------------------------------------• Reagent i·J ei ghable ron~ pH Remarks Metal/ Reference He tal compl.ex Factor

--------------------------------------~-- .. ------------------------------------------ ----------I II III IV v VI

------------ ll __ .._ ___________ ,.. ____________________ .., ... _____________________ --------·-·--·- ••• -

Potasdum CUSCN 5-1 Pb(II), Reagent excess, 0.522lt 11 tbi.oeyanate HOj Jaterf'ere

o<- Benao!Mxiu cuce1"-n,1o2B>2 3-7..6.0 Zn(II), JI1(II) Jabrrere o.aaoo 12 Ja IUIIIDOilical. a41\11l

8allC71 al.do:a:1ae cu cc716o2:to2 a.6-3.a H1(II), Zn(II), Co(II) d• n•t interfere

0.1892 13

8-H7dro!I qujnolJ.Jle CU(C9'1J60N)2 (8-Quin 1no1) 5 ·33·1"--35 Mb(J:I) interferes 0.1806 ,... 15

Qu1na1d1n1e acid Cu{C1gH6C29)z•Ra0 B2~ medtua Pb{II~t H&(II), Cd(II~, Zn(II J Mft(II), Ni(II t As(III , U(VI), P"431nterf'ere

0.1"-92 16

B-Ii;rdro:z,'•ll•lfutnJ'l.• CU(C2oH1fllia>a 3·1-11.0 .. o.o951t- 17 N~aylben.-.id1ne hydrochloride

)t

l\: C1 0:

U.BL.I 8 (Com'D.)

--------------------------------------------------------------------------------------------------I II III IV v VI

---------------·--------------------------------------------..---------------·····--- -·-·--- ··--AllmoniUIIl tbioe)'Mat.e

CuflCN 1:1eakly acidic Co(II), Ni(II), ~(II), 1Hd.1um 1m(II) interfere

Aaaaon!.um thioC78Date and p)'ridine

fcu(C5"~N)2l(scN)2 Neutral and Cd(II), N1(II), Co(II), l :I veekly ac141e Zn(II), r.tt(II) 1nter.fere medium

1 ,2,3, .l:lensot1'1asole -

N-m-Chlcropheayl- (C1*n11no3Cl) 2CU -~ybenso-hJ(I.ro:lamic acid

?.o-s.s

3.S-4.o

Cd(II), Zn(II), Co(II), Ni(II) interfere

Pb(II), Hg(II), Ni(II), Zn(II) 1 Mn(II), Cd(II) do not interfere

0.5221+ 16

0.20?8 16

- 18

0.1030 -···--------..... --.... ·~---·---------..----------- ---- ---• Other aethodsa ~Ca'1t. (9); 'fhtGDa]1de (9)1 Arlt:hl'8n1llc acid (9h

Eth.71ened1am1ne and mereur1c iodide (16); Benzoyl. acetcme (19)1

Hydrogen sulphide (20)J 'l'hioaeetollide (20)J

Resacetophenea (21) J Th1osal1cyl.1c acid (22) J

a.. Chloro a,s dtaeth()27aeetoacetan111de C23).

N crt e.g

m 1ooa wch aa lee4, merou17, eadlWit aino md -.m••• do

not 1ntertere. The reaaent 1a also IUitallle tor aranmetl"1e

eaUmaUcm due to the h11b .eleoular' ve1Pt et tbe OtiiPlu

and the low coover•1cm raotora tor oobalt and copper.

Cobalt and cGpper oan be aeparat.ed 8D4

determined w1t.h N-m-CPMBHA m pre1ence of aweral to:re1p

ions. The p:rec1p1tatea are directl.J weishable tJlel'llau;y

stable, have high molecular welsh' vi th lov eooverai•

factor. several oOIIlllCm tl_.w aoaall;r uaoc1at841 with

cobalt and copper do not interfere. The procedun 1111

s1mple end the re&&ent. tan be pnpared eaa:U;r ancl s\o:red

1ndefin1 t.el,J'.

1. Majlllldar t A. K. t "tl•Ben.cO¥lphiUI1lJITdftq1 em:J ne 8ll4

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