Polarography of the cadmium and zinc xanthate complexes

ELECrROAtiALYTICAL

CHEMISTRY

Elsevier PublishingCompany,

POLAROGRAPHY

OF THE

HIROSHI

KODAMA

Departme+

of Chemistry.

(Received

June

INTERFACWL

FacuZty

209

IdXTROCHEMISTRY

Printed in The Netherlands

CADMIUM

KENJIRO

AND

10th.

AND

Amsterdam-

AND

ZINC

XANTHATE

COMPLEXES

HAYASHI

of Sciesace. Hokkaido

University,

Sapporo

(Japan)

1966)

INTRODUCTION

Bivalent

xanthate

cadmium'

in aqueous

and

Zinc

foqn

sparingly-soluble

sol_utionl~a. .It has been found,

diskolve in the presence of excess-xanthate_ zinc form w+ter-soluble complexes in 0-I M

precipitates.with

however,

ethyl

that the precipitates

For example, 5 - IO-SlWcadmium and and 0.3 M ethylxqthate, respectively.

In the present study, the nature of the water-soluble cadrniurn or z&z and xanthate has beeninvestigatedbythe

complex

formed between

polarographic

method

andtheover-allformationconstants'derived_ EXPERIMENTAL

The potassium

ethyl

freshlypreparedeve~~fewdays

xanthate

stock solution

(Tanaka

Chemicals

G-R.)

was

andstoredina-stopperedbottleprotectedfroklight_

The concentration of this solution wasdete rmined gravimetrically as-copper xanthate. Cadmium and zinc solutions .were prepared from their nitrates and sthdardizedbytitrationwith EDNA. Gelatin, at a concentration of o_oIO/~ in the firialsolution, was fetid s&sfac-tory as maz&num suppressor.

210

EC. KODXMA, The

"halfiwave

p&entiat"

whichi.%

definedinr~yer&b2e-wave

IL

HAYASHX

taxi b.e eva.luat-

data_ by applying the M~ITSUDLI~A%&SE e&~~ti&~ (Fig. z)_ The plot of the hal-kave pc&enti&' against log ef the xaqthate concentration. gives-a straigI$ line_ (Fig. -3)_-It is, therefore, reasonable to conclude that the complex

tic%fbk

these

.

I

Fig_

1. The

relation

-085 EvrS_CE_ between

soh~s; xanthate~concn.

log

t

I

t

-GBO

i/~i~-i)

0.1, 0.4.and

1.

-0.95

-0.90 : and

potential

for

cxduxium

xax&.hate

cdmplex-in

aqueous

1.0 M.

zTy-fL_ ‘CEEI

I

-o_eo _...Ifig_ 2. Tl+

‘complek

relation in aqneuus

-..

-085

En S.CE ~txvt&n &ektial and s0lr1.~; xar+hate c&x.

I

-OS50

I

~_-095

E+(Z13~RTfk~ o. I, 0.4 a&

log

1.0 M.

i/(-

sd~i)

for _

cadmi_um:~anthate

POIXROGTXAPH3f

The

equation,

OF

slope i.e_; fok

cd-

AKD

%‘k-XiXNTlW2-E

COMPLEXES

211

of the &tie-in .Fig. 3 is IZO mV; .which gives xanth&ie ions/cadrni+n io& &~the coznplex_

a v<ie of 4 for p in the

The expressions

a’ value of 1x3 x 10 11. for the xanthate complex, CCI(~~ZHEQCS&+_~

gave

over-&

forrna~iori

consta.nt

-085

Figs. 3-i_ Plot of (E*), as a function bf x%thate aqueous soln., (4) in non-aqueous soln.

concn.

for cadmium

for

-0.90~

kanEhate

the

cad_mi&

70.90.

coghplex;

-‘(3) .:i.i~

H.

212

KODAMA,

K.

HAYASHI

Evidence fbr the reversibility of the polarograpbic reduction .of catium in the mixed solvent was obtained from the follow&g- experimental facts: _(i) the temperatnre coefficient for the diffusion current was z%/degree; (ii) plots of log i/(&-i) US.E gave we&defined straight lines with a slope of 22 -E_ 2 mV_ J-he overaIl formation constant and the value of p mere evaluated by -the metbod described above_ A plot

of (E,},

against

log [xanthatef

gives

a well-defin&~.straight

line with

a

of 93 mV, which leads to a value of 3. I ( = 3) for p (Fig. 4) _ The over-all formation constant was estimated to be 2.5 x 1014.

sIope

Expeximents

were

performed

with

3.0

x

IO--“&X

zlIlc

k

lithium

chloride

electrolyte. The concentration of potassium ethyl xanthate was varied frozn -o.oz to 0.5 M, keeping the ionic strength at 1.0 by addition of the requisite amount of Lithium chloride.

supporting

The

The polarographic reduction “‘half-wave potentials”‘, (I?,),,

of zinc in xanthate were obtained by

medium was qtiasi-reversible. the method described above,

A plot of (E& against log [xanthate] gives a straight line with a slope (Fig. 5) _ The values of p and the over-all formation constant were estimated x ~9, respectivelybe 2-g (= 3) and 426 86 mV

REFEKENCES

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