Specific effects of neutral salts on the rate of ionic reactions in solution

Presented for the Degree

o:C

UNIVEr?.SI'J!Y 01" Nl~Yr ZI'LALAND

(}

THESIS

___ _..___,._"_"•-=,,-$4-....--..w<;t.c,~-"*'-'~-"'•'~---~~---'~~-_.,.., __ . · "

-

:r.ntroduction

. . . ...

The a.ction of the thiosulphate :Lon on alipl:latic haJj.des

The JJ:cl)nsted equ~o1.tion

...

Speeif'ic interaction of ions, •

...

Previous work on the

b:cornoacetate-thiosulpha:Ge :ceaction. , . P1an of' \lo:dc

. .

.

...

.

.

. .

..

Preparation a:nd purif:i.ceJ;ion of materialn •••

.

.

.

.

. .

...

Calculation of rate constants

...

Discussion o:t' results ••

...

.

..

Summa.ry

... .

..

.

..

'l'ables

... .

..

. ..

. .

'

Bibliography

...

.

.

.

.

..

G:caphs

. .

. ... .

..

--o--1

2

8

16

lG

20

21

2'1

33

0

A

Na-Na :ceaction

K-K

:ceaction

Na-K :ceaction

K-l\fa rea.ction

•••

...

. .

'

...

...

...

...

conceni;rat:i.o:n of A.

activity of A

a.ctivity coefficient of A

C)

mr. ··· ionic strength

:ceaction between BrCH"OOJ:C c1:

Nans

2

o

3

6 f-J LJ ~J

--o--PHH:IlffiY SALT l~li>P.J':CTS. ---""'----~~

It ha[:! long 'been knovm that the rate of a chemical reaction involving :tons in solution is a function of the total elec)crolyl;e cm:J.co11tra:\;ion, even in systems where the:ce is no

whe·thex· tho ions are present as roact;ants or pur•ely as

Quan·t:tta·bive :i:oi'ornw:Gion about thi~J ef:t'ect cannot be obtained from every reaction, a .... s tho theoretical treatment, as well as the e:r:,perimental method imposes ce:ct::d.n l:i.rrd.'tin.g co:nd:i.t:i.ons., .A ~:mitablo reaction must occttr at a measurable rate vr.i:bh no complicating side reactions and back reactions,

and without change in :i.onj.c 8trength,. Mor·eover there must be a quick [:;1J.1.d accu:cate method of analysing the reacting mi:xture

2

-has shown tha:t reactions of the type

I t

I?X

+

~~,<-> H S,.,O.:z

+

X

t'J tJ

where X is a lw:logen and R an aJ:lphatic radical, o.:co simple

substitutions, remar.!Gibly free from side reootions o The th:i<osulphate

radio:).]. becomes attached to the carbon of the aliphatic chain through a ~mlphur atom ..

Slator used reootions of this t;y1x3 ·where H v.ras an alkyl group to measure the relative reactivities of tho substituted halo2:e.ns. lie then e::c'cend.e<1 his vrork to )Ghe cvBe ·where I?X was a halegono-tl.cotate,

and made the first measurement~~ on the bromoacetate-i;h:i.osulphate :co n.Dt ion.

This reaction

'

.B:r.CH2CX)2

I

-->

t320301I2C02

I

+

Br

is typiqal of the class 0 It is a simple second o:r:·der reaction, ::mel sat:L8fics all the cond:i:t:i.om; for a reaction suitable fo:c kinetic

'rho rate constant may be readily s.nd fairly accurately dete:r.'mined 1Jy titrating the u:n:r.eactet1 thiosulph~~ce in the solution vr.i.th :i.odine, usin~ sta:cch solution as 8X1 inCLi.cator, and calc1J.l£J:cing

k :f.':r.'om the equation

:x:

k ::::

at

a-x

vvhere a :i.s tho :i.niti:il concentration of the reactants, a:nd x the aJ1101mt ·bhat has reacted at D. tim<-) t. 'rhis equa.tion is applica:ble

-

4·-'J!he reaction bet·ween the bromoaceta'ce ion a:nc1 tho thiosulphato ion may lJe forrmJ.lated in te:cms of the Jcransition sJcate ·theory, as taldng place vlith the formation of an intermediate complex •. :1£

I

BrCH

2

co

2

+

X

I I I I I

s

₂

o "'cn,po

0

J t.J ( J ,:_j

I

+ B:c •

• • ( 1)

111

567

The critical complex X ' ' cor:cesponds. to tho maxirm .. m1

potentj.al energy attained by the system as it passes th:cough a series of states, as the reooting ions appr·oach, interact, and finally g:i:ve

the products. All ·these j.nte:c•mediate states are of lovrer p:cobab:tli ty

than eHher the inHi::.u or final states, so tha:t it may be assumed that when the system haB p~3Bsed through ·the transition state, the least proba:ble o:f:' them all, the ).~eacrtion is completed. ~.'he activated complex behaves in most :cenpec:tn a8 an o:cdina:cy rnolecu1ar. spocieu. Its forrna:t:.i.on involves the usual changes in free energy, entropy, etc. , and all the rotational ancl translational energy states

are

distributel1 in the same ma:nncr as :tn an ordinat·y molecule or ion :i .• c. the potential energy. :Ln all these states is a minimum. One of the vihr.atiorwJ. s{;s;tes, however, is exceptional in having the potential

energy a ma.'::imum., This state has become what ha.'3 been called an intramolecular translational state, . and it represents the rrntion of' the pa:cts of tho cm:rplox relative to one a:rwther, co:c:cesponding to the reacrt:i.on about )co take place o It is th:i.s maximu)n potential energy which leac1s to i;he low p:cobability of the conplex.

to reach the 81:UYJO conclusions by treating the activated complex as a

molecular specie:ci, and pictu:cing the re21.0tion as taking place j.n two steps. Tho first step is the formation of the complex from the unactivatecl molecules or ions, and the second the decomposition of X 1 1 1 _{into the products.}

I!'or the gcneraJ. reaction k2

A + l3

C

+

D • • •(2)

using BrUnsted' s original ·!;:cea~~ment, it is at3~mmcd that a statisticaJ. equilibr·ium exista between the reacting molecule and tho activated complex X.

i.e.

_{• • • 0}

₍₃₎

where K iEl an equilibrium constt1x1JG o 1'he second J?:C'ocess, then, the

decompos:L tion of X. into the product a, is the rate-determining process , so that

• •

•

( 4-)

Then, aasurning that k2 is a canst ant independent of the env:Lco:nme:nt ,

fAi:ll

fx

( 5)

If the reaction :i.s 8econd o:r.d.er, V o: k₁C,AGB • 0 • •

(6)

ana

combining

(5) and (6)

!!J:i\~

fx

k 0

st'B

_fx

.

.

.

• ('1)

This equation cannot be tested experimentaJJ.y a.s it sta.YJ.d.s, but if the activity coefficients carl be expressed in measurable quantities,

6

-ph;ys:1.e8]_ moanirl[~ only :in cases where zA + _{z13 ::: zx •} ~Phis is a

nece::;sa:c:y conditim1. of' the t:cansition oomplox:, so tha:'c the .Deb;ye-liuckol

limiting Javr

f,. A . 2

-Jog J. ::::. ZJ.~

( 8)

may be applied, and

log kt

=

1ogK₀

+

2A

z

₁₁

zp;"'Jit. • • • (

9)

log k

~-'his equation has been tested :Cor :numerous :ceoot:i.ons by measuring

Jche :cate constant at (l.iffe:cerrt; ionic sb:·en[!;ths, and plot"l;ing log k

against~ • Jn gene:cal :i:b ifi found thrr'c at low :i.onie st:cenc;ths,

1 • J..l l · · ·'· SIAL 0 the :ce.suli; .i.n,P_,· curve becomes

a.nc :1.11 ~>.1e __ JJ,n v a ;--~·~> t .. J.:tnesr, and the

slope is the theore-t:;:Lcal value ZAZ13 but t.lJ.at ::rl; higher :i.onic wc:cengths

c1evia:c:i.ona become appa:cent, a:nd the slcY[.lC faLLG off quite qu.iokly.

.. "' a

,9

V. K. l.Ja Jter studied the var·j_a:llion of the :cate constant of the

reaot:i.o:n between the b:comoacetate ion c1nd the th:i.ormlphate ion in the

presence of dif'fere:n.t tm:i.va1cmt o<:ttions. In Hd.3 oase, Jchc curves

:3.-ppx•oxim::ltcd to the same straight line with slope zAzl3'" 2, at; low

concentra:tions, 'but as the ionic sb~·cn1->;·th j:nc:ceased the c1i.screp::xno:i.erj bocc1me very rrw:dcod., and specific eff'eciiG develoJ.led i.e. tho cv;rves for

the sodium ancl potas,s:Lum cations no 1on;::;er; coinoidccl. It is n:op::1:cent,

t.herefo:ce , that the equation

log k

=

log K.₀

+

2~.

does not deGc:c:i.be omlple·i;ely ·the

o::rl;n,lytic e:f:Ceot of the ion::! in sollJ.tion on the

e:x.})e:ciment is as rnuch a ·test of the Dcbye-Huckol limiting law as o:C tho transition frtate theory, and :Lt is generally ass1..U11ed ths:t the o1)served d:Lscreponcies m"'e due Jco the failu:ce of the limiting law at higher ionic strengths, a.nd do not reflect doubt on the essential co:ercctnerm of ec1uation (

'7).

of the law.

The Debye..:JJ{{ckol limiting lav7 is ba£Jed on the assvmption th::r'G

the:ce at•e only simple Coulombic forces acting on D:tl. ion in solution.

If '(;his were b:'ue, the primary salt effects of all ions :i.n

solution VvDuld be deter:m:ined. by the:i.r concentration Dn.d ch<:l:Cge, and

for a pa:ctieulor reaction and temperaJcure, ·l;he plot o:.C log k agr:d.nst

1Jl'

wortld give an identical cur·ve, however the ion:i.c sJcrength vrer·e

'.Chis, however, :l.1!3 not the ca.se , exee;;pt at very low concentra:tions, and it is necessacy ·to poutulo:te seconda:cy fo:c·ces exe:cted by ionB, depending on their inclLv:tdual pro~pe:ct:ies.

The:cc are nume:cous examples of spce:Lf:Lc effects of ions :i.n

solution, and it is elear that the act:iv:i.:l;y eoeff:i.eie:n:l; of nn ion is a function of Jche ionic env.Lconment, and is :not inclcpendent of

the

iom; with which :i:l; is assoc:i.a:l;ed,

as

the p:cinciple of ionie

r~trength implies.

•• 10-16 . J • I . . . . _

Bx·onsted f:trsc :ur,roduced h:w p:c:mciple of specJ.i':i.e

:b:rLeraction of ions to a.ecomTG for the vveight of expe:cimenJcal

evidence vih:ich did not fit in w:Vch the prine:i.ple of :i.ndepended;

1 1- .. 1'/ Hl,l9

act:i.vi ty eoeffieients of ions developed JY .. ,i.ael:rmes and Harned. ·

}iiaeinnes had postulated that the aet:i. v:Lty eoei'fioienb of cations anci.

a.n:i.ons in the same solution mey differ f:r.om one anothe:c, and that the activity coefficient of the chloride ion ;;:d; any given coneentrat:i.on

is independent o:C the cat:ion asc:JOeiatecl vlith i t .

Dronsted ea:cd.ed out a detailed exam:i.na:l;ion of act:l.vity eoeffieien.tn by measurements of ao1ubi1ity, and :E'ound tha:t the

solvents. On tho basis of these and other observations, BreJnsted

formu~atecl his principle of ;:~pecific inte:caction o:C :i.ons. The activity coefficient of an ion, then, i:.:; a function of the nature of the ion :i:tsolf', and of' tho solvent contain:Lng it. In a dilute salt solution of constant ~cota:L concentration (most of' this theory Vk1S developed ·before Levrls ancl Hanc1a116 introduced the concept of ionic strength) ions vr.i.ll be uni:Cormly influenced by ions of their ovm

sign.

Bronstecl ascribed these specific effects to tho individual. cho.r·acte:c of io:ns, a;pp:ceciable even at low concentrations. He claimed that the deviations observed in freez:i.ng point measu:cements, cou1d o:nly be e:x:plained, if' complete d:i.1.:wociation of the s a1·ts vrai:J assurned, <¥:! be1ng the result of' a r;econda:cy poYier exerted by an ion 3

a power vvhj.ch ca.n exert a specific action on ions of the s<Jme or· o:t' ano'che:c type., These secondary forces, a<;co:cding to Bronsted, Clepend upon the st:cuotu:r.o and size of the :i.nclividual ions.

If' these co:nsider~:ttions are applied to the kinetics of' the br·omoaoetate-thiosulphate reaction, the deviations from the

Bronstect-Debyc equatj.o:n may ·be expla:i.ned :in a qual:i.tative 1nam1er. It is impossible to define the oxac·t coni'ig<Jration of the t:r.ansition comr)le::x:, ·but it has certain esaential chs:cacteristics vihich are knovrtlo It is the state of lovrest p:cobab:i.li ty of the syatem, it is 1.1r1.dorgo:Lng an :Lntr::unolecular translationa1 motion, and it is triply nor!,ativoly ch<:\:cged. Hence tt may be picturecl as

10

-consisting of' a co:ce of' poaiJc:Lve nuclei and a negative charge

d:i.st:cibutiono Orient:c1:'Gion of the solvent molecul<:;s in its immediate neighbourhood Vi:i.ll stab:Ll:i.se i t to a certain e:A.-ten:t.

If a cation a;pproaches the comp1e:x:, the e:xtranuclea.r eloct:r;ons which a:ce be:Lng attracted towo::cd.s Jche positive nuclei of' ·the

constituent atoms, vrl.ll he attl.'o.cted in the opposite direction.. As a result ·the structt.tre 1V""lll become rnore rigid and consolidated, and the potential energy will decrease • Since the only st::1:be :i.n wh:i.ch the potenti2~ energy is not alreac1y a minimum is tho intramolecu1::.LC Jc:runsln:'d.onal sJcu:te, the movement of the purls of' the complex

relat:i.ve to one another ra.ust 1Je inhi h:i.ted, and the JX:Co bt~bi1i ty that the syster:1 w:U1 cx•os::; the ene:cgy "btec:eie:c is dec:ccasccl.

If, on the other hnnct~ an anion approaches the complex in solution, :th1 ncgat:i.ve chanr:;e will repel the cloct:co:ns ~ so that two fo:ccos vii11 opo:cate v.pon them simultaneously in the same d:i.rection.,

~.1_he

result will be an inc:cea .. se in potential energyo

It

is

now necessa:ry

to

consider tho :probability of either

of

these interactions oomxrin.go Since the cha:t"'ge o1:' the transition complex is eque~ to the sum ol' the clwrg<:;s

of

the reactants

;x

in this case vd.11 be t:{·iply negatively charged. At any inshmt such a Sl)ecies mnut be s1.xcrouncled in oolution by m1 excess of posi t:Lve

:tom-J

o 'rhe probability that an anion ·will app:coach clo~3ely enough

to intc:caot ·v:r.i.th the complex is very low, and one VJoulc1 not exped; the second :interact ion to oocu::c. 'l1_{ho stahiHs:i.ng action o:C ·the}

cations 1 hov.ove:c, vr.i1J. opera"ce, as i;he complex will have a munber of

' 'I ' i'"' t . }1PV'C' c'·l~l0 .!:>1. • e·re11t C' 1ec·t"•''On a·f>.L·"':.t' 1·u' .L\• ·i e" , t}·J.e

SJ.nce c_::L· ·I eren · J.ons ~" ... ~ ~ GW. .., ._,

deg:cee of the two effects \Vi11 vro::y from ca)c:Lon to cation and from

anion

to

anion., lf it is assumed that anions cannot approach the complex closely enough to :i;nteract v.r.i;th i t , it follovm that aLl

anions vr1ll influence the corrr1Jlex un:iformly, and Jchat specific effects will :not be appa;cex/c • Cations, hovveve:c, w:i.ll have inc:cea..~ing

stabilising cfi'ec·t in the o:cdex· of increasing electron ai'f:i.Di tes. K+

<

·w •. _.r~d..

+(

r·

_;J.. .+·

The stability of the complex is rcflectecl in the measured reo..ction :catc, vrhich is determined by the ra:te of decomposition of the tra:11Sit:i.on complex into the products. Hence :;m:i.ons should Ghow no specific ca:tatylic effect on the reaction :cate and oationG should have increa~Jing catatyl:Lc effect in the order of decreasing electron

Ji+ ,

>

''f + 1'

a

>

.

T .J], .+

When the~Je comliderations m·o e:x:·tendocl to polyv::JJ.ent cations there is Emotho:c factor ·which must be accounted for. ht lilo:c a;ncl Fessenden9 in studying the of'f'ects of diff'erent cations upon the bromoaceta:te-thioGulphate reaction, found. that in the presence of

divalent eo:lJions :3uch as calcium and ms.gnesiu:rn, the velocity increa.acd fax· 1nore :cap:i.dly with ionic strength than. wa.s calculated. by the

Bronsted-Debye .equation. The cu.x'Ve obtainec1 by plotting log k

against~ had. initially a slope grea:ter than the theoretical value of

2..

vih.:ich f'ell off quite rapidly at higher :i.onie strengthso

12-of ·the complex, a lov.re:c vaJ.ue than that calculated by the l)ebye-Btickel limiting law. 1'he corresponding decreases in £'₁\ and. fn

are not ::luff::i.cient to counterba~ancc the decrease in f:x:, so that tho is greater than ·the calculated

fx

value, and the vcloci ty constm.ts for the reaction are greater than

Jche corresponding values f~or tho reaction in the presence of

univalent cations.

It

is

impossible, therefore, to predict the relative effects of a divaJent and a univalent cation .. There are ·b1o opposing faoJcors to be oo:rmic1ered, and oi tho:c Bight predominate. Jilor im:rt a:nee,

although tho man;nes:'Lum ion ha.s

a

greater electron affinity tha.n the potassium :i.on, is found

that

the reaction in tho presence of magner:d.wn ions :Ls faster than in the presence of pota•Jsium ions, i.e e the second effect is g:cea:ter.

It is pos::::d.1:>le ~ hovrever, to compare the effects of a series of Tho order of :i.ncreasing elect:con a:f:'i'inity a cleoreasing ionic :caili.us "l'rlll be the order of deorear·d.ng catalytic effcqt.,

Processes involving the fonnatio:n o:f. a highly :nc[!;atively

9hanged complex a:ce not comr1o:n, so that it is dif'f'icul

t

to cor:cela:l;e the specific effeota olmer"Ved in the broll1oacetate-th1osulphate

reaction vrlth suff:i.eiedc :i.ndopenclent <lata to make a geno:r:·a1i.;-;ation

(

I I I 'Z'j' I

2 Jre ON)

6 ·I· v ..

in chan.g:i.ng f':com sodium to potass:ltrrn salts, but that in gcmcra1 an.ions in:t'luenced j_-t unifo:cmly .. llo_v . reover, _Jus·G -- ' 21 _s l 1ow e _C• ~ .1-1 u _{:1a:c G ,} J J he ve .. oc:Lu J · J-y

of the :Corvmrd reaction w;;VJ aJ.v1ayo g:ccater :in the presence of

potasshun ion than :ln the presence of sodimn ion ..

Bek:ier22 studied the kinetics of the :ceactio:n between the chloroaoetate ion and tho thiosulphatc ion. Ile fotmd that cations

. ++) ,.,

++' ()

++'\. ,,- ++

and Ba •:>r

1

a 1 ·'1_1g

a:nd attr•ibuted this specific catalytic action to the Cl:i.ff'er:Lng rnob:i.lit:Lcs of' the cations.,

'l'h:Ls ::;c:d.es is ·paralleleCl in the :ccaot:i.on betvreen Jche persulphate ion and the iod:1.c1e ion.

It I I I I I

:32°8 _{" L} + 2J -~---} 2SOL1. + 12

I.-_mre. 1 • 'Ll- 23 , 25 _d showed that the salt effe(YtG or oat:i.onfi deo:ceaJ3e in tho order

He po:tnts out that thin is nJ.so the order of' r1eoreasing ionic :cacli1..1.S ~

n:nd of'fers "che fol1owlng explanation.

14

-is lower.

This explanation, based on the collision theory requires that the eno:csy of ac·t:l.vat:i.on should increase on changing the cations in the react:Lng Hystem f:com potassium to lithitun. The a.1terna·te

e:x:pla:r1ation is baseCl on the tra.nsi tion state theory, which according to La hl:or :ccqu:Lrcs that the entropy of' activation is tho main factor influencing the change o:f' reaetion velocity with ionic strength.

Thir1 may be pict·ured in the following way.

It

was seen that the close approach of a cation to tho complex in solution causes a decrease in poten'ciaJ. energy l'Y inhibiting the 1nt::carnolecular

tranalational motion .. Since the format:Lon of the complex, and its passage across the ene:cgy bar:r."ier• entail a redist:cihu:t:i.on o:f:' tho energy of the reacting anions, ax:w f'ac·tor complicating this

ro8:c:cangcme:nt will eause a dec:cea'.>e of' orJ.tropy :Ln the formation of the aet:i.vated complex, and the reaction vr.L11 be ~llowe:c. 13uch a factor is Uw interaetion of cations w:Lth the complex. One might ex:pec·l;, ther·efo::ce, ·bhat tb.e entropy of activation would becorac more negative, on changing the catioml in the reacting system from

potassium to lithitm1.

I·l; shoulcl' be intere[;ting, then, to compare the variations in

entropies and energies of activation of' the reac·l;ion a:t the s,8.lTIO

ion:i.c strength in tho p:cesence of potassiu.rn, GoClitUJ1 and lithiu;n ions. In tho Ar.rho.niw equation

-:~!:act

k.:::::d...e

""W

Eaot or log k

=

log

cA. -

~1'

J.ila.ct

the B factor corrLa:tns a probab:LJ.:l.ty component, snd is therefore a measure of the err'cropy of activation. V. K. l1a He:c mearnrced the rate consta;nt of the bromoacetate-thiosulphate reaction ovex· a range

of temperatv.:ces, ::mel calculated the cme:cgies of activD:'Gion f).nO. the

B factors at different j.onic strengths. He pointed out that the Arrhenius equa:'Gion requires tl:w.t increasing ionic. st:cength shoulcl increase the energy of activation. 'rhis leads to a conclusion, vrhich

is in acco:r:d with none of' the acc1Jmulated data on }Jrima:cy salt effects,

that tho addition of neutral salts should dec:cea::;e the rate of a

reaction. JJa Her po.stula:'cod, the:ce:t'o:ce, that the B factor decrea.::1es

:c~:cpidly with increasing ionic strength, and that i t is the entropy, and not i;he energy of activation ·which :Li> prec1om:i.nD.nt ly 8J'fected. by

:i.onic strength. IIis ex:perimental results appear to bca:c out hi('>

theoretical p:ccdictions, but must be inter'I.Jretecl cautiom~ly, as the

o:cder of accuracy of' ·both E and B is necessa:d.ly 1ovr.

'rhe problem of' tho specific cation effects :i.s merely a special

case of the more general J):r:·oblem of pd.rna:cy salt effects and it is a

corollary of )Ja Mc:c1

s hypothesir:J that f:lpecif:Lc cation effocJcs result

16

-1 2 2'7

'.I~he reaction has been studied by Bla:'cor, ' ' l<:capavin, ' j

..

1.1 e,o,26,28-3o. 31 32 ₁.. 3~i

Ja 1.er, Ka:m:>a:r1.na, ' \.J.ss, and otherr::l.

1\:r.'a;r>::win measured the r·ate of' the Na .• Na reaction hi. the presence of sollium nitr·atc, chloride, iodide, and sulphate. The va.luos of the ra:te constant he obtained sugge[~t very stronr;ly that

anions ha.:ve no specific action on the reaetion rate~

1\appa:nna sho·wed tha:(; the temperabrcc coefficient is independent of the ionic strength, and that i:n gene:cal, the effect of a change j,n temperr:l.tu:ce is in accord with the Br,.onstcd-Debyc equa:'cion.

V. K. Ija Mer and co-v<Orkers h::we ~;tudied this reaction ver·y exten.s:i.velyo They showed that in the p:r.e;Jence of univalent cations ( God:i.um and potassiwn) Hw Brb"nsted-Dobye equation. :i.s obeyed a·t low ionic: stren,P;ths. The C1JX'ves obtained by plotting log k + 1 against ~ tend to a stra:Lgh1

c line w:i.th tho theoretioa1 slope At hie;her va.lues

oi'fo,

hov;eve:r:, the 8lope falls off quite rapidly, and specific effects develop ] .• c. the cu:cvoa for the reaction in the presence of' sodium and potassitun ions no longer

coinc:Lcle. In the presonee of' divalent ca-t :ions, the D:conatec1-Deb:re oqv.ation (':oeG not holct even at Jovr concen:t:catio:ns, nnd again each cat :Lon has

a

srlecif':i.c ef't'ect.

I1a }:;or· aluo studted t.he kineties of the reaction f'rorn the point of vtew o:C the A:c:chen:i.us equation

JJ k :::

r:/...e

-HT

Ho me:::t81J.:ced the Y.'[l_te constant of tho :coaction D;b vn:cy:Lng in:i.tial conccnt:cat:i.ons of' the reactar~.ts, and in the p:r.eGence of

high-~valent S8J:ts uuch a.s bm'icun and lanthanium chlo:t":i.de, a:nd :in the preGence of non-electrolytes, ove:t.• a r·ange of temvera:tu;.ces.

on

1.

the

..

I!

+

no

::l.n

The effect of added caesium, potassium, socli"Lun 1:tthimn, bar:bun, strontium, calcium and magnesium salts o:n the Na.-Na, K-r;n, l'Ta-K, rrnd K-K reactions ·was measured.

'rho rate constant f'or the ~-Na reactioxw in the p:cosence of adclod salts were measu:ced at 25°0 and at 35°0, an.d }J and J3

calculated f'rom the equation

20

-B:comoacetic Acid.

~ '~-=~,_-.. --~--·=""---~-,;.·-~~~·-·

Bromoacetic f).Cid vras p:cepHxed 'by the 'b:cornination of acetic acid

i11 the p:ccsence of acetic m:1.hyclcide. 'J~he impLJ.:co p:coduot v1as

pu:c:U.'icd by clir:;tilla:tion. 'rho final :f':caction collected bo:U.ed at

~!he pu:city of' t:b.e oorrt:,;oou:nd W<Cl.S tested by titration

with o.:3N

:::odj:un th:i.oaulphato, aa under these conditions tho :coactiun

is complete in tvrenty-fou:c hou:ca, and with 0. 2N sodimn hydroxide.

The :catio of :ceplaceo~ble bromine to replaceable hydro::,;en ±':com theBe

te::d;EJ vraB l.CJ1, 0.97, 1.011, 1o03, O.D9 in five c1cto:crninat:Lo:ns. ~l'hc

purified p:codnct; was

kept

ove:c pho;:>pho:cous pcntoxido in a de~;:Lcoator.

with d:i.stiJ.Jcu vm.tec. '.L'lte thior:lulphate so1utions we:ce stab:Lliscd by

the addHion of a little bicarbonate.

The nout:cal ;:1aJ:k~ added to the :cea.ctantG wer·e a1r>o

or A.n.

quality, o:c v"e:ce recryut ,;t11:Laed.

Oaeaiur,l ch1o:c:i.clo IVGf.l f>:Cepm-ecl f:com tho dichlo:c-iodide by ·t:ceo.:ki.r.t,g

i\. f':ce~1h sta:cch solut:i.on was p:ccpa:ced befor·e each :cun, f:com A.H.

'J:he initi8..l eoncentr~=tt:i.ons of the rc8..c'cants weJ:o kept a:'c O.OJli in al1 :ceaetions. '.rho two solu·tions vve:r·e plaeed in the thermostat 8;n<l

the eqv.i vaJ.cmt volume of thiosulpha(;e pi petted into the hcomoacetate

solut:i.on v..ilCn they :c·eachod the equili1)rium temperature.

haJ.f-dclivc:c:·;r of the pipette was taken as the in::i.t:\.n.l time of' n~actio:n..

At inte:cva.ls aliqv.ots o:f' the :r.eactio:n mixture were :cernoved, the roact:i.on sto}_)))l'"t'l vrlth iodine, and the excess :l.odine baek titn'l.tcx1 vr.Lth thiosulpha:co

solution.

The bromoacetate solut:i.on for each :cun was made up by dissolving

Jche weight o:f.' bromoacetic ad.d in vratm:, neut:caJising vr.:i:l;h potaasicun or sodium hydroxide, usin;~ phenol phtha.lein as in.dico.tm::, ancl diluting

The th:Losu1ph8..tc and Loc:tino IJoll.rt:i.oml vrc:ce

broEJoacctic aei<1 tested f:com time to time. \ (T'•J· J, ~ • 1-:l co c"t-'J ci ~.., -~·to+ . v v··:.-"" · ~~,.,( .._/ o '1 I

It V/:313 i'ound thLi..t the most WcuraLe method of cu:r.:·:cyinr_:; out the

tit:cation;:; was as J.'ollovm. il.liquots of' bees. vre:co r-ouovec1, and ·l;he

reaub.on ;3topiJed vli.th ~/,cos. of' iodine [>olution, a.pp:coximately .o~:n;.

These quantit:l.en we:ce chose:n. so that tb.c iodine eould be added :cap:i.cl1y,

thus rD:f.nhd.sin:·; tho er·:co:c :i.n time.

It waD found, too, that the :ceaul ts V£\:d.ecl wl th the c:oncentrat;ion of the added thiosulphato solution. Du:cing tho t:i.t:ca.t:Lons 8:tr:Jos;)llc:c:i.c

oxidation IJocmao a;:•}xceci:3.ble vrith t:i.me, so ·(;hat :i.t vm.s em,;entia1 to

j:·un in the thiosulphatc solution qu:i.ckly. 'J'hin c:c:co:c vras loant YT1th a

snwJ.l voluwe ot' eoncon:'c.:cated thiom.tlphate. If the E;olution vras too

- 22

tha·c tho lJest col!lp:colflise vras a .Oll!1 solution.

In o:cc1e:c to 1~educc tho e:c:cor due to nt;l;I01:1phe:cic o:xida.tion f\rctlte:c, a:n approx:i.ma:te value :fo:c the :Ct'l:Ge constant was found fo:c

eucl1· run ( eithe:c by analogy w:i:tlt other :cesults, ox· by cn:c:c,<,d.:ng out a trial :ccm) and the app:cox:Lmate volDJne of' thiosulph:xbc 'Nhiell Yrould be :cequ:Lre<l ·to :ceact vrlth the excess iodine calculated :t'm:· :cegula:c )cime

inf;ervnls. Under these conditions all but about .02oc of' the

thiosu1ph~x'ce could be run in directly, a:n.d the);e wa!3 not t:i.mo for

D .. htN~phe:cic oxidation to eause apprec:u:tblo e):·ror.

\'/hen the tib:·a)dons \VGl"e car:ciocl out in t11iD VID.y, and the sta:cch solution. added when on;I.y about .o;~cc oL' thiosulphB:'ce was to

In the

presence of b;,l):·:i.um ions the co lour of' Jclw st <:~:r:•ch-:i.odine ::;olut:Lon.

changecJ, ixrt ·(;his did not affect the end lloint.

~rhe method of studying saJ:'t.; effec"cn by· adc1in.<; ncut:caJ. flalta

to the :cem::tants, has seve:cal l:i.rn:i:b:'c:i.ons. :-):i.nco the :ceac·tion is one of sinrole suhd~:i.tution

If

+ ~3;;;03

I

+ E:c

otlw:c anions in the solution may react vrith the 1n;->omoacetate ion in

DJ1 m1alagous lna:rmc;c. 1'his vd; 11 not cmv:-w <XJlp:cec ial)le e:r.To:r.· unless the :cate of the seconcla:r·y reaction :La co;npacablc with tl1at of the

1)J:·omoacetate~thio;:rnlphate reaction. That h:yclrolys:i.s of' ·the

-the pr·erJcnce of' .OG}l 1Jm:·:huTl chlod.de and

.om.;

1D:n-thaniurrl chlo:cide

on tho gnmnds that the reaction.

I I

l3:cCH 2

co

2 + Cl ~~) GlCH 2C02 + J3r

Ui:.1 :cc[;u]:b for· the :coaction :Ln tl1e p:couonce of Hodiu1:1 nit:cato a::co

open to a sirnila:c o:ci·l;j_oisrn.

no

:cecords values for tho r·a:te

coswtant :Cor a :ceacJcing soluU.oil 1.1p to 3L in so<1iur;1 n:Lt:cate, and it

has been 1'ou.ntl thG:c tho x·eaction J.a not st:c.i.ctJy second orilo:c :Co:c

co:oce:nt:cation.s gr·oate:c than abOLrc .02f5N :in lJaTiok) •

It Vfi:JJ:l found that moklt ardons j~·eacted to ;:;orne extent, but

that the rate of tJJ.o Gocondtu:'Y :ceaction;:J vras no·l; appr·eciabJo in the

Only the b:comide :Lon could be u.sed over· a

:C'OErb:·ieted by the w.:>o of iodine in mear;ur:!.nr; the :ceact:i.on :co.to.

'J:he nitx·ito ion, for exa:rnpJe, c:ou1d not lJe used, as i·t :cotl.C·te<l

vr.i th the iocl:i.!le •

~.'he choice of cations, too, was somcv1hat reGi;:cioted. :Llany

of the heavy meta'L b:co:noacotateG 8J1.c1 th:LosuJr>lJ.;;d;os a:ce :i.nuolub1e /

~

21-At each tine into:cva1 Jche rate com~ta(lt was occluu.latcd f'rom

thG forrnnla

where a ia 1

Che in:aial conoent:cation of the :ceactcm"cs and. x J• .u c• tho

amoudc that h;::trJ :coacted at a ·bime t. ,

It o;m.s esf3ential fo:c thif1 vvo:ck that 1

che :ca:'Gc con:3tant for tho

reactions :i.n the 1.:ibscmce o:r added salt should be b:loVhl as uccu:c·o.tc1y

as pos~nblo. J.;'o:c the lla--lifa x·eact:i.on, tl1e Vt:l11.J.c:: at initLil

concent:cations .,OJ.lif h8B been va:ciously 1:·epo:cted a~> ./.l4b, .!J:511· artc1 .4:'1'1.

'J'hia me:::u:>uremcnt, thc:ccfo:ce, was :cepeated, us:i.nr; :fJ:•esh thio:::mlphate

and io(\inc solutions each time, until a rosul·L :ce-~JJ:'ooueiblc w:i:chifl

• OOJ. was ob-tained. 'l'ht:Jse va.lwx~ are shovm. in '.L' nlll8 ~2 •

~I.'hc 1no~~t accu:ca:'cc value of k L'o:c each :coaction V/Ll...':-1 calculateCl b,y

a method Cleve loped by Roaovoare. ~,'he integ:cated equation f'o:c a ;::;econd

o:cde:c :c·o::;..ction ·vihon the :i.n:i.t:i.D~ co:o.con:t:c·~-~,t:Lons of' the x·eaotantB a:ce

eqy.al :1s

[~

_%0]

1

-k

...

t

where C is the concent:ca;tion at a time

t,

an.d C₀ the concent:cat:ion

Th,e p:cobable er:co:c in concentration, x·, :u:> smaJ.l coritpa:cecl to

the concent:c::d;ion, and the:cef'o:ce m·1e may usc the r1e:c·:Los ex:pan::;:i.o:n

l

_.1

_-·

:c

()

+

r·LJ

"" -1'1

-$

-·

C-r.·

_c

(JL-1 c.:)

.

• •

.

and neglect all excCJYG

tl-le first ·GYro te:r~rns.

l X'

:in

Let v _.J :::; n _'-'O

I

then 1 ..

-

-'-conoontr·;J.i;(' on wLll be l

(r

₀ )2

+

:r.'k ".

t

Cao2)

I

l

an.c1 k t ::;:: 0

-

0 ₀ 1

~

'2 1

'l'he p:cob~tble Oj:•x·o:c will be a minirm.1m when

i.e.

or

-vJl1en

+

2y:::: l ·c· 2

·o _{'"' 2 .&o}

In the thiosulphB:Le-b:r·omoac:etate :ce ac:Jcion, the t:bno-erro:c is

negligible :Ln compa:cison vdJch the conc:ont:cation e:c:co:c, and ther·e:Core

i t may be assumed t1w;t tl!.C e:cTox· r is solely due to o:crox' in

concent:cal;ion. f.iince the rll:·obab1e er:cor in concenb:·at:Lon, :ins·coad

4

Hence the condition for minimum e:r.nl!:in k :coduces to y

+

2y - 1 i.e. y ::: .36

This rnew1s that tho uost accu:cate value of the ra:Le const;;:~.nt wilL be

tha!c ca1culatcd for vrhen about 36/~ of tho thiomJ.lpha.te has :ceac·Lecl.

In ~p:cac·~ice, the ave:case of :cute oonstrxnt calculated for s:Lx

time inte:cvals WG.s ccJW~JiJ:ced with. the value fo:c v1hich the f':caction.

vihicit h<3.d :c•eacted vVaG noa:.cont to • 56 •

26

-neoeG:3a:c·y, a:n.d tha;l:; in alJ oru:JO:J the value for y~. 36 r;ave r,1ore

~rhe ro.sults obtained fo:c typical runs a:ce Ghmvn in ~:able I.

'l'he rnosJG a.ccu:ca'Gtl!!k-values ( CfJ~Leulatecl by Hosevea:ce 1

G nethod) a:ce

given i11 ~: ables ~J-6, m1.d the gra:phs shovr the cttcves obt a:!. ned by

plott:L:ng log k + 1 agaimrt ~

The <:li'fCJct of a.c1ded soc1ium salts 011 the reaction betvreen .01].1

sodium b:comoaceJca:te and .oJM sod:i.m11 thiosulphate is shov-m. in g:caphs 1 and 2. Yi:i.tl·1in the limits of expor:i.rncnJc a1 erro:c these cur'ves

reacrl;:Lo:n. vrLth vacying :i.n:i.ti::LL concen:!;:cationrJ of the :coad;a:nts,

(graph ~;,) •

i:nchuled. Vlhen potar;uinm ualts we:co adued to the same ini tia1 COTJ.cent:ca.tiom1 of the r'CD.ctants, the cu:cves shovm in f•;r'a:pll8 3 D.ncl t),

1\.e;rtln these curves a:ce ident:i.ca1 vrith one another,

but the:y a:ce clistinct f:com the fonner set of cux-vos. Prom a

col!lpariso:n of these SEYCf~ of' data it is ev:i.<.1ent tha:t the roa.ct:Lo:o :i.s uniformly ca"caJysed by rrn.ionG but thfd; the t'l7o cations shovr ::;poc:H'ic

The ::wne concllwion is :ceD.chod by a s:Lr:1ila:c t:cea:tment of the K-Hc u .. -·(·e~ctl· .1(~~ L·)n ( ."::;.~ rrr"nl1c• (_1,.1 u (. 11-8') 0

Id.th:i.1.JJn nal)cs v1e:ce found to be Elll exception to thia :i:~:tle.

G·:caph ~-l shows tho of'f'ect of added lithitm1 chloride and lithivm

sulphcJ:te on the ret".ction otc. 'l'be dcvolopmorrc o:C spec:U'ic an.i.on

effects he:r:·e n1ust be due in some way to the extronoly small :cadius

of' the 1ith:i.uiJ ion. :Ct could, of cou:cse, be expla:i.ne(l by

28

-imp1y that the other alkali metal su1phates ;:;1.:ce comj_)lc?cely clissoci atcd, as they ll::ow·e the S<lJ,Je. catal:'rtic effects as tJJ.e co:c:cesponding clJ.lo:ciderJ,

~:he:co iG no doubt, hovmvo:c, that this method is not sens:i:tive

e·nou;~;lt to detect inconpleto c1issoc:iation in salts -v7hose deg:coc o:l:

Jis:3ociEJ:tio:n :i.;:; ve:cy clor.:Je to one. It ir~ possible, tlleref'o:r·e, ·that

·the effect of incomplete clir.:mociation can be detected only :i.n the

case of Jj.·l;:tt:i.um, vrhich has a ve:cy much st:co:ngex· tenclonc,; to J:'oxTn

In r;:capl:l ll the e:f.'f'ccts o:C added potam.dtml and sod:i.lm1 salts on

the ITa-l'Ta ancl E-h: :ccactio£18 8:t"'e compared., Ji'o:c cu:cve I , the only ca:tionG in thu solution were potasc~io;n ion.s, and i'o:c curve IV sod:i.m1

ions. Curve II, Ghovrlng the ef:Ceet of added :potnB~lium sDJ.ts on the Ha-TTa :coac1

cion :i.G neon to :c:i::;e steeply initially, and a;lp:coach

curve I c::t:s ·che :i.on:tc :::1t:cength increases, i.e. whe:n t.h.e pot:::tr;:::;:i.mn ions

s:('e lo:cge1y :i.n cxcens of the sodium ions. 'I'ho aclclition of soditu·n salts

to the K-K :ceacticm has the opposite c:Cfect. ~L'he r:·;r•ad:Lo:nt of' cu:cve IJI is 1oVJe):', a:nd tho cu.r·ve approacheD tho Na-.Ha cu:cvo D.t hicl!e:r:· ionic

:~:<'o:c the I'la--E reaction tlle :c:::ttJo oJ:' potarJc~iwn to ::;odium iorw of

t11o :ccacta:n.t~J ia ~3:1<t 'l'he curves, therefore, lie clouo:c to the L·-L

cu:cve 1

Clw.n to the i:a~TTa cu:cve ( e;:caph l~J.), and curve II fmJc:.:; with tho

K-K CUTVO. Cucve JIJ c1oe~; not fuse with the J!a-1°la Ctlrvo, bu·t

approaohes i·(; at l'd.ghe:c ionie st:ccngths.

'l'heao ef':Cectn are :r.evex'sod in tho K-Ha :ceact:i.on (.c';J:·aph 13) vthe:ce the ro.:tio of pot:::tssimn to socli1.-un :Lorw inib.al1y :is 1:2.

l'':con UteGe :ecsuJ.tu it appear·s that the c:xtalyl;ic cff'octs of' the i;vro c:J.t:i.o:ns o:ce a:_pp:co:xiuatcly additi vo o

.

A rno:ce dc·tD.ilec1 analysis of' these j~·esulta :cevcwJ.G a aimplc

additive rela;t:'Lonf.llli}' bcbree:n the logarithims of the :ca:'cc

K-1\.

··.r y

.li8.-~\. K-lfo. Iia-l·ia

-Jff-.2 ' ) oLJ <) •"-' .2

-

30

-J,g.g__J-:;,·r.J.

o691 .G85 .680 .6'/o

c

_>')r + C' _J]\T +

-. .::.';__~~-.-~ .• ~L~~

.03 0

.02 .01

.01 .02

0

.u::s

In each C8IJe the rerJ1acement of .ol Na+ by .01 K+ h~J.S inc:ceaf\0(1

the logar.Hhium of' the rate constant by about

.oos.

The :;:yj:ccernent

obtaincci. here in p:cobably fortuitous, as the differences involved are ve;cy smaJ.l, and the rate constants a::ce not known sufficiently accu:c:ltcJ.y fo:c mu.ch wciglrl; to be put on .!che thi:cd I)lace of the

log k:+l values o

It seems appaco:nt, howeve:c, that the Silcni:C:ic natalytin e:Cf'ects

the K-Ila :ceaction. In both cases ·bho catalytic effect :i.nc:cea~3os in

the o:cde:r

'l'hat anio:nn catal;yse Jche :coaction unir'or1:1ly, except Vihen

as::weiatucl 1'/:ith li ch:Lum ion.

effect in the o:cde:c of irwroa;;:dn.'£ ionic :cad:ins.

univalent c:.OJ.tions, :i.:c:cespective of thei:c ionic r·ach:t.

1_{1! able G shows the values of' B and B of the equation}

B "-""""'""'--..

--

...

log J::

=

E\ ~· ~~ .3R1

r

calcula:'ced i':cm,1 the ra."Go

Jt is clear· f:com an inspection of' these re::oults that no definite conclusion om·1 be :ce::J.Ghed.

An e~cro:c of one percent in the value of k leadLl to an er:co:c o:C about

~~00 calo:cJ.ea J.:Cl the ene:cgy of acU vation

rJ,

and of D~bout .13 units in

B. Bince this J.s tho o:cde:c of acourac::r of the menSlH'Ot1 rate cone:;-[; a:ntf.l,

it iEl ev.tdent that 1..1.soful values of l~ anc1 B can only be ob-La.incd by

t

aJd.ng the a:ve:ct:\f£0 of a ve:cy large munbe:c of' mcamxcementa •

. An iJJ.te:cestine; point OL!O:cging f:com the measm:-·ements at the

hiE)1.c:c telilpe:crJ.tv:ce L3 that tho eorx·er:Jpo:nding values o:E' J: for the

:ceac:Lion in the :q:ccscneo of' li thhun chlo:cide and lithium ,'JU1p1mto n:ce

tho anions associa:l;ed with the Jitb:i.lun ion seem to be cl:i.sa:ppem~in.;( D.t

higher ten]le:catur-es. rt:his is to be expected if' the ef:feotfl m'e

attributed to ·[;he inc0lrl}11ote dissociation of' :U.thiurn Gulphate, since

the Cleg:cee of cU.flGOCiation WouJ.l'J. p:cobabJ.y :i.nc:cease Vt:Ll;h irw:co as:i.ng

' )

( J 0

b:coJnoacetatc ion and -~he thiosu1phato ion have been moasu:ccd by the method of adding neutral saJ.ts to the :ceaobxnts at constant

J:t has been shown that anions

cata1:yse the :ceact:i.on uniformly, except vrhon -Ghcy ~1:cc associated Vii th l:Lthhun :Lone

S:pec:i.f:Lc cation offeets have been shown to :Lne:coase h1 the order

·'·+)

++) C'a-

++)

VDlcnce t;y~pe i.e. the o:cdor Ba' S:c ·

and Cs+) K+ ) Na+) ld.+

J,:r(f++ ·''b

3. A·.n explan~dion of the ~}pacific effectn obcJerved hoB been oJ:'fe:ced

and compared w:i.th the a1:te:nl.ate explanation offe:ced by Hovtells.

4,. 'J:lw one:ce;y of aeti vation and B facto:c have been calclllaLed i':com the

Aliquot:~ of 'L·. r,-;~nec. vre:c-c removed at time :intc:cvals, the :ccaci~ion

sJcopped. v1ith 1.983cc. iodi:ne, Lmd the solution bad::-t:Vcra;l;ed w:Lth

thiormJ.}Jh8.:to.

(a) With no D.dded salt.

Iodine solution 0.0203N

1~iwe

Mins.

<30

7]:~x ()I/. uo (\r· .Jt) l05;~.

~ r~

llb

.1.3 • 21.5

.42

C:"l" Ol)tJ o66

.'75

.221

.253

.:no

(b) In the presence of .Ot32[)N I<:Br.

~J.'ime

Mins.

3'1

r;o

GCS o oOlOGli

or·

• .J

(>~14

.11:4:

6 rA

• c)

.[31 .99

<) X X 10"'

• 201);

.21_1/1:

Iodine solution 0 .020:3l'f

'.eime oc.o:LOml

55 .Q()

'15 .31

<.17~'

.4·1:5

95~~, .1:59

113 .'72

126 ' .,8<1:

n

X X 10CJ

.20'7 .2!59 .295 @312 .31·9 .~!'15

(b) In the p:ce~lerwe of .012N. llaCJ

ce.01lN ,h. X 10

2

56

.n

e21(3

t!5 .24

I 'I

!4:~E .;:)6 • 2'1 ,'3

86 .-'J:8 .299

91:5

.59

1i

10 ':~ .69 .::546

.-'.l·'74: .4,6'1 .4:78 .4'/!J: .<1:74 .11'/6 ""'-~"--4=--"'-""

_

.. 1 .

lc:::~ ~\!c

.49'7

.502 .b01·

.50!J:

Hatu CO~tU:.d.; ar1t f'o:c the :r·e 8Dtion between sod:Luirl b:comoaeeJcate tl:d.osulplw:te in

tho

netrh·al sa .. lts at 0

:n1c.L soili1Jm ~presence of' 25 C~

a

_·-

l1 :::; .OJJri

1 k =at

.

a-x

.· -' 'l 1 (i,.l

~-j;;_~~~':)~Gl::~-~

_)%

l:.<?.K-Ls.-!·1

fiE

fL

fZ

J

0_JL.l:::!:I

C) _.6'75

.2 .6'76 Q ~~ .. _.6'/5

n

v· .675

0 L/

LH

•"'

.. 2 .671 C) _.W/9 () Jli.'L f,tlO

.2 1' .6D'I

6 ,-:, _•"-' f.! ~-;.;U

IlaJ? e 2[)1 .?29 .231 .'108 • 2~~(3 .704 .216 .6~12

II _{.2.09 .684}

NaC1 .250 .• '12'7 • 2tl:l5 • '1~10 (t~~36 $'/12 e~~2FJ .708

II _{.224 1\o702 • 2lt!: .689}

l'iE~B:c .2Sbl .1304: .3~52 7()<) 17 ()0

.'790 .30[) • '1'!5

$ oJ t:..J Gdt:JO

II _{.. 280 .niB .265 • 7 4~~~ 6 ~[jf) er/3!3 .2119}

.?2B

II ( ) ' / ' )

f}LidLJ ,.'11.0 .221

,CDS

.209 .685

liDJJO.., .21·9 • 72'/ .23[) .'7J1 ')nLJ _{.703 .2~30 .697}

G LJ r.:1 .~-:

ir 0

• ~'.l6 .C-390 .208 .681],

rfo..2~30tj, _{.2;)5 .'713 .23[5} .K

.'713 .:,~25 .'701 .21<3 .696 • 207 .6130

KOl

.250 .'736 .244 .'729 @ ~~~9 .7JA: .224 .'/07

II _{.2~U1 .693 .,209 .G£3?}

1U3:c .3()4 .,84:1 .3!11 .s;J4 e5<LS .8;:;'; ·e;j;j(-) ₈₁₈

r?,qr4

\) (._JutJ ,810 .014- .'199 _$:5CJO .. '7(16 _{~290 • '7'18}

.2'79 .7G7 .26:5 .'750 e251_{J .'!!J:O .236}

Q 7~]1

2'"->

lb L.itJ .'701 .217 .69\J

K:r:

.~329 .714 .220 .'701 .~ns .GD~~ .210 .G89

Kl

.,20'/ .685

l\J~03 0 ~?,31 .. 'fl() .225 .'lOG .2JJ) .69!5 .:.--~13 .G9:3

FJ·lO 3 .210 .690 .209 .686

K2~l04 o ~?,LJ:l "'72'7 .2:1o .713 .2~~2 .'704 .21!5 o (}\JLl

.209 .606

JO;:i.Cl .249 .'719 .236 .'10'7 • ~~2'/ .'/00 .~ll9 $(.)D3

•

~n..o e683

Id.2SOLJ _{.210 .'705} • 2,'32 ~700 .:326 .G9Ei .220 .21[5 .690 .209 .G\YI

CsOl .251 .'151 o2<l:ZJ .'143 .23fi o'73J. .~~28 .?23

0 ~326 ,'/20 &215 .699 .209 .6%

TlaC1"

"'

• 2110 .'162 .231 o'I!HJ .220 .'12L"i o215 .'715

fU

Yft

~

rfo

f>:c01 2

.250

.'770

o2-'!rl

.753

f)()f)

• LJ t:J (J D ?2~3 .210

.GDG

Ca01 2

.24.-G

.755

.235

.'73'7

.226 @ 7~32 • ~(LO .6\:.JS

OaBr

_{2 .251}

_.'760

_{.~mo .'1?.9 .221}

_.'713

_{• ;:;ug .6913}

r,r:c{a~; _.24C")

_.'741

_{.2?>1 .?21· "2~J5}

_.715

_{.21'/ • '?O?J}

lr oJ·.'fo from La lVIex' t EJ data K fr•o1n K:ca:pavin 1

- 38

Rate conr;:;tants f'o:c the :ceaction betvree:n potarwhun b:comouceJcat;e

a

_-·

b =

.OlM

1 k ~ 2tt

e2 .691

_"

.G90 C)

.C'S91 ' ) _.GSD

•"'

•'" •"'

.2 .690 .2 .fj~jQ u.6

_"

.691 QO ') .Gf36

l'Ja1h: .061 • f>ltl: _{• 0;) .•.} o t-LL

.2310 0 3tJ:l .eo~5 0 :j(J() .'199

II

o322 .'190 .310 • '7LJ!J.. .,300 • '/'I !5 ~28;) • '7'/0

II _{o2r/5 ,'/60 .2G1 • 7iL-9} ');) 0

9 '-' ~:o'LJ

.·;.:w

fJ ')rlrJ 6t)t) .'/21)

0 ~~21 .7lo .21'7 .'/10 .209 .'701

J\11:c .364· .[)45 0 2)!)[) e [);:~.;) () ~)<1;1 _• [) v _L!U ~· _.anu f / 1 . ' { ) .82G

.320 .8?,1 .30[) .809 0 ~~~95 .'19'1 • ~~B~ .7[)!5

.270 .774: .2b9 .7()3 • 2·1:G .'749 $ 2:5'/ ~'/4

1\.atc constant :f.'o:c the :ceaction betw-een potnssium b:comoacet8:'ce

DXJ.d God:i.nm thiosulpha:te in Jche p:ccscnco of ne1rb:ca1 salts.

a=b=.OJJ:I

•

J:=

at

::t-:x:

flL

l.o..g_l:C±l

'}#

_"r

jii

"

.680 <)

.681 .2 .C3UO ~2 .6130

• t:J oLJ

.2·1:1 • '7 :53 .::~3'1

.n:Jo

• ~~ ~~~? .71'/ .220 .'70'7

II

_.211

_{.696 .~~09 .Ei9!3}

•. 35~1 .83'/ o QLh'/ .E330 e :5:)%

.n2o

.3J[)

G ( - ) ( ) ( )

ll

.307

.800

.297

.'/93 ')'JC'l

• ~-Jo.._~ Q '/81_{1: .2'70 .'16Li}

0 ~~Ll1J: .'l!l-8 .i~oe $'/32 &Cj~{5

.'!lG

.21G 0'/0:J

il

.:,no

_.69b

KJ Q ~~:3~)

.no

.~ns

.7CJG

.~no .'195 .209 .694,

.~~4·0 o?03 'J'JI/

t}(:~t,)c..) • 7~JZ) &i;6'/

.71B

.:211 .:.JDG

II _{.200 .6D4}

0 2{t:ti

.'736

.238

.731

0 ~ ~;'1 • 'I J.G

.:n::J

.'106

.209 .EJ9t3

0 ~:~!4?

.730

.~?.0? • '/:21 .~3~~~9 .'713 • ~~~ fiO .'103

HaB:r. .2i60 .808

.253

.804 .349 .(302 '/'()()

oOuo .?f3'1

.2i08 • 7'1 i3 .2BG

.'/61

0 ~~~'/1

.751

• 2C.\t1, • 71:5

.24-U • '130 .237 .'720 .2~~G .708 .2lb

.CD7

.~J:LO 0C.iD3

• 2Lr:Ll7 .'/30 -~~)2 • 'IJ.b nc-;()

e f-.lt·~u .7L; .214:

.6DG

.207

.Gf39

• ~~(L-7 .700 .:24:0 .724 ; ) c·,o

o tJ,-~o .'I:Ll e~~le .'100

II

.:;::w

0(:)93

Oo:o.td.)

log k ;:;; B - 2.

oalo1JJa:l;ed i':com the :cate constants of the Na~.]Ja :c·e::lo·Gion in t;he

.,,

J!l Il

.2 .6'7b 1.05'/ 160~-JO JJ .l] .. f>

.6n'5 1.053 lbBSO ll. :)2

.G'/5 1.0[)3 1513()() JJ. & 2)~;

.24b YTl:c .'7?.9

1.10'7

J5D90

JJ m 3iJ

24:5 KG:c .'/29 J.lll 1Ci0:3o 11.4·9

JUl:c .'729 l.lll ].(:)030

:u .

1_1.-9

NaT.\:c • '/~30

1.100

159'/0 JJ .• 11.-:;:;

.'72.0 1.100

1ti9'70

11.·1 .. ~~

• 24t>

.'715

1.09'/ 16050 11.4-9

.'715

1.093 l!5Emo ll. ~3G

.'111 l.O~K:5 160b0 lL48

.'Ill l.ODO 1!5890 11.36

.24-5 _{.'111 1.090} J.L'if390 1J. .;:SG

• 2C:i5 .'151 J .1)50 15920

n .'to

.2G!5 .'751 1. J.~:iLJ.- 16090

n.

E5!5

.265 hl3:c • 7!51 l. J):i1_{t· 16090 lJ} r· h

f)()t)

.265 • '7!1:2 Ll2J. 1!50:),0

n

.1-3

1. S1a:ter ~foCoSe 0~

~,:~' 1286 (1904)

2o Glater J'

.c. s.

8'7

-·-'

4:85 (1905)

'/. _{H:Lnshel wood Arm nep. 211}

332 (1927)

t ) .

--'

4.

Bell Arm Rep. _-~~~' 36 82 (19:59)

t-'

o. Pola:nyi and Hinshe1wooc1 ~foCo~)e' 140629

(19::\'1)

6. .E!yring T.J~oSo' _u:;:, ''-11 _{1 ( 19~)8)}

'7.

Bell

~fcCo~3o' .,;;,_~~.?.

·uw

629 (194::>)

8. La Mer

J.A.c.s.,

_5]~' 3;)41 (HJ29)

9. l;a JvJ.e:c and J:i1_erssnden

J' .A .C. S., 1-L1

;;

·"'

2351 (1932)

10. B:r:anstecl

J.A.c.s.,

_:~, '781 (1920)

11 .. BronB)ced J· •. t1..C.:::;., IL3

"~""~' 2265

(1921)

12. B:co·nst e d J·.A.c.s.,

_.1&,

8'77 ( J g•>n) .... f-ALl

13. Bro'nst eel

.J.A.c.s.,

1 I"

!:::_:~' 28D8 ( 1923)

14. Bro'nstecl

J·.A.c.s.,

j:6, 55;) (1924)

15.

Brons ted and Brumbough J" .A .c .1:3. , lj,(1

<--4-=.,.., 2015 (1926)

16. Broi·J.S"t ed and r~ivinr:;stone J·.A.C.~3., 1-9 ~ 4:35 (19;3'7)

1'7. Hacinnc~i ,J.A.C.S.,

_.:k1,

1086 (1919)

lB.

Harned

_;J.i\.c.s.,

Ll0

..,_~, 1808 (Hl20)

19. Ha.:cned. ~e &.It1 _~

s

0 , (")'?,:

"''~'

462 ( 19~)'7)

20. Ija llierl ·and l•1

r:i edma:nn J' oJ\ oC~ 61Jo >

J2£:!,

8'/6 (1930)

21. J'ust •7

/J. Pbys:Uc Chem. 6'" d

1"'1/..(l

;:)<)U (190D)

22. Helder _{:R.oczinki Ohem.} ]_(1

"'~·' ₍₁₉₀₆₎

64-23. Howells ~foCoSo :> ).4-2:,' 463 (:LD39)

24. JJowens

_J.c.s.,

26. I, a He:c and Mi ld:ce d B • Iummer 2'7. l.;i>apa:vin

28 .. I;a Mer ::mel }.lildred 1~. Ka:rnnor 29. JJa Eer and l.iildred

:m.

Kamne:c 30. J.~a lier and l.iildred B. Kamner 31. Kapr1a.nna

32 • l\.:;1.ppanna and 1-'atvra:cdham 33. Kiss a11cl Vass

;54,. Hoseveare

7.. Physik Chern.

§Jl,

1~'\\J

~r.A.c.>:J.,

.01,

2()62

J .• .A.C. 8., 5'(, 2tl?2

(1935)

( 191~1)

( l\0:51)

(1035)

(193!5)

,J. Ind. Chem. iJoc. §., 45 ( 1920) ~r. lnd. Chern. Soc • .Q.,:''.\79 (H)32)

Z. ano:cg all gem. chem.

(] ()'!.f)) ~ .- '1,),(-J

r

•v

look+•

'

,,,

'

' ' I

,

Jo,~K-t• .~.s

I , ,

• Nlltt..

•NRIIIn!> ·•

• NFJBR.

• KBA

i

Louk+l

T

()·~Si

loc-.l"+a.

I

o-8

o-b•---~~---~---~~---0-l. (l·l

I K-K Read

ion

vJi th

a<ided I'o~cri.sHi :3a1)tis II Na-Na Reqction wl-tL added Poto.sG;ium ~Jp.lts

HI I\.:.1\ l{ead;ion vfith ao,cled ~1odiuriJ ;:~:a:J.:~s

lV' Na-Na Hoaction with adde<;1 Socliun1 ,'=)alts

O·b. L-~---__;,---'-'----..,-.--.---,--'-.,... ______ ...,.._._.,.:-'"" _ _ ...,.

Ol.

1 Jt.;..J:\. I~eaction

vv:Lth

added l'ota9.a:l.um E?a:Lts

l;fa-K .Heac·tio:n, w:j,th. · ackled Po't~\Bs:l;qm ~)a::Vcs

Na.-K Heaction vr..tth acldeCl Sodi\.un

do.lts