288 ANALYTICA CIIIMICA ACTA VOL. 13 (1955)

POTENTIOMETRIC STUDIES IN OXIDATION-REDUCTION REACTIONS

XX. REDUCTION WITH FERROUS ETHYLENEDIAMINE SULPHATE INDIRECT DETERMINATIONS

UAL\\‘AX’I- SINGH, SURJrT SINGH AND HARBANS SINGH

CARAWAY AND OESDER~ have prepared ferrous ethylencdiaminc sulphate, FeSO,. (CHa.NMa)2S04.4H,0, and sllowcd that it reacted stoichiometrically with standard solutions of three powerful oxidizing agents, namely, potassium dichromate, potassium pcrmanganate and ccric sulphate which arc commonly employed in oxidimetric titrations.

In acid medium ferrous ethylcnediamine sulphatc reacts with potassium pcrmanga- nate, hydrogen pcroside, potassium persulphate, potassium dichromate, potassium chlorate, potassium bromate and ceric sulphatc?.

A known wcigl:llt of cncll substance was mixed with an cxccss of stikndard ferrous ctl~ylcricclian~iric sulphatc solution and tllc mixture ncidificcl wit11 sulphuric ocicl. I’llosphoric acid mixture was used in tile cnsc of potrrssiuin pcrsulphntc, potirssiuln chlorntc :~nd pot:issiurn brornatu. 5 to x0 ml of %irnnlcrmann’s rcclgcrit wcro ills0 ndclcd wlicn tllc mixture containctl potassium clllorntu or potassium bromotc. ‘I’lic niixlurc contairung potasviurn clilorntc way llcatcd for about ten minutes to SO0 C

Releretlccs p. 232

Fbtassrum permonganate ml -

1’: IKlO, F ICl3r0, G Cc(SO,),

VOL. 13 (1955) POTENTI03fETRIC STUDIES XX 2%

TAIILE I

Titration of 0.01235 g of potassium dichrcmatc mixed with 5 ml of water, 20 ml of o.ogN ferrous cthylencdiamine sulphate and zo ml of 4N I-&SO,. against o.ogN potassium permangnnate solution.

0.00

I .oo

3 oo

6.00

9.00

II.00

I2 00

13.00

14 00

r4.40

X4.70

Ij.80

14.90

~445

Ifj.00

rs.05

15.X0

15.20

x5.50

x6.00

17.00

IQ.00

22.00

25.00

o.39g2

0403 I

o.4r37

0.430 I

0.44%

0.4Gr 0

0.4704

0.4815

0.5007

0.5x38

0.5300

o*.54* 5

o. 5695

0.6o2 I

0.9534

o.g6Qo

o.g803

0.$?gG

1.or44

1.0305 I

I.0495

I .oG87

x .0830

I .ogzo

4

5

5

6

7

9

XI

19

33

53

rr5

280

G52

70zG (maximum)

312

22c

93

83

3‘r

r9

10

5

3

in an ntmosphcre of carbon dioxide and then allowed to cool. In each case the c.xccss ferrous ethylene- diaminc sulphato was titrated at 20~ C against standard potassium permanganatc solution by a potcntiomctric method. The mixture was kept stirred by a mcchamcal stirrer during the titrations. A bright platinum foil immersed in the solution to be titrated was used as an oxidation-reduction electrode, and this \vas coupled with a saturated calomel electrode throqh an a#$ar-agar potrrvsium chloride bridge. During the titration the progress of the reaction was studied p3tcntiometrically. At the equivalence point a sharp jump in potential was obscrvcd in each titration,

Re~ererices p. 2gr

290 13. SIXGI-I, S. SIXGH, 11. SISGH vor-. 13 (rg5S)

A scrics of potcntiomctric titrations wcrc performed with different amounts of each substance. One titrntion, as typicnl of the set, is recortlctl In Table 1.

All chcmicds, cxccpt ccric sulphatc, used in tlus investigation arc of guarantcccl purity. Ccric sulphatc was stanclartlizccl with pure arscnious oxitlc 3. twccn x ant1 2N in the potentiomctric titrations.

Acid normality of the mixlurc was kept h-

Phosplloric.ocicl mixture wns prcparcd ly mixing 75 ml H&O, (Sp. gr. 1.8.1) with 75 ml H,pO, (Sp. gr. 1.75) and diluting it to 500 ml with distillctl water.

The titrations, one for each substance, arc rcprcscntcd by the curves, A to G, given in Fig. 1.

Jn these titrations .it is cvidcnt that with the addition of the titrant the E.M.F. rose steadily till the ccluivalcncc point. At the cquivalcncc point there was a sharp juxnlj in potential followed hy a steady rise in each case.

From the amount ot potassium pcrmanganatc used, corresponding to the ecluivalcnce point in each titration, the amount of ferrous cthylcnediaminc sulphatc recluircd for the rcductionof cachsul~stanccwascalculatcdar~dconscquentlythcamountofcacl~sul~stance was dctcrrnined.The results recorded in Tables II -VIII show that potassium dichromate, potassium pernlanganatc, hydrogen peroxide, potassium lxrsulphatc, potassium chlorate, potassium lxomatc and ccric sulphatc can bc detcrmincd indirectly by the potcntiomctric method, using ferrous ctllylcnediaminc sulphatc (lT5) as a reducing agent.

0.0123 0 0243 o.03.13 0.04.l L 0.05tJ0

6 _ _ _... _..__ .

0.0088 o.or33 0.01~)0 0.0229

0.027G

If.0. Inhwr

R _. ___. _ .._ ._-_-__

0.004 I

0.0047 o.ooSY 0.0x13 o.orjj”-

20.00 I ,).‘Jh fj.o‘to 0.0123 20.00 IO.036 cJ.()G.+ 0.0243 20.00 5.902 14.008 0.0342 37.0” 18XJ8r I&.01() O.O.).+O

.p.oo 1 23.918 24.082 0.0587 -- .-.-- -----_ ---___._

‘I’Al3[,1S III i’OTASS1Uhl I’Ifl:hl~NGAKAT&

r\‘/:tl i:i:s -

_--_-_ . _ _ __.. . - __.___ __.__

N/m 1iJfu0, N/m I”l:S rcdrlrcl usrll lot used /I)

K.\f #IO* /owlcl

c,ccss 1:i:s WI ml

IiMtrV, ntl R . _ .._ -._ _- __ . ._._

25.00 rcJ*45’J 5.54 1 0.0088 25.00 16.555 8.445 0.0134 25.00 rz.t~rl!, 12.031 o.oxgo

25.00 IO.512 I+188 0.0229

25.00 7.5‘11 I7.459 0.02-/G - . ..--. - -- _ ..-. . .- - _.__._--- .- - -.._ ._ _.__ _ . __.. _. _

TAl3Ll5 1v IIYDROGON 1’EROSIDE

__ _-._. . __--._ _ __-_ - ____ - ..-. __- _-.-- -_- . . .- ..- .__ ____.._ _ _ __ __ __ _ _ __.__ __ __ N/m l;i:S N/m h’Al110,

c1111lc11 trscrl /or N/l0 FBS ffd-4

c\ccss I’HS usal by /ouwl II,O,

,,I1 ml ml R --_ _-. .-- __-__- --

25.00 ao.a.to 4.7h 0.004 I 25.00 19.3rr 5.G88 0.0048 25.00 14.G8g 10.311 0.0088 25.00 11.7G1 13.239 o.oxr3 25.00 7.140 x7.8Go 0.0152

.-.-._---- -_--- _- -I

VOL. 13 (1935) POTESTIOMETRIC STUDIES ?Ck 291

TABLE V

POTASSIUM PEHSULPIIAT’D

h-,.5.0, /ortnd

N/~aofEs

R l?tl . - .___ .--_-.__-_ _-_----- -..- ---

_ _ hw;. -. .- .-__.__..-_-_.. ._ S/JO I’ f..S

1aktn ddtd $ ml

__. _ __ . .

0.00.5!5 25.00 0.0072 25 00 0.0114 25.00 q.0143 25.00 O.OI’)fj 25.00

.i flrf,;

_ S/m f**f:‘s

1akcn uddd fi .‘c I

.._ --__- -.- - _. - .____ __. . ._.. - . .

0.008~ 20.00

0.0 I.)0 20.00

0.0170 20.00

0.020‘# 33.00 0.025.t 42.00

N/x KMnO, turd Nlao I*‘lL5 ustd h-&o, /or txtess FES by fi,S,O. taken

ml ml 67 _ __..- -._----_- .-._-___-__ __- ____ -._- ____

20.994 d.OOG 0.02 70

18 048 0.951 0.0470

’ 3.954 II.O.lG 0.0747 I I .oG7 13.933 0.094 t

7.456 17.54-# 0.1rSg

__. ._ _.--_.--..- .-__ - -___ - ._ . ..- .- .--.._ -- _ _-..-- _.. _ .._. -- . .

I’OrASStUZf CHLORATE - ____ -_- _ -- -.-... _ _ _____.._ _ _-..______-__.- _____ _

rv/Jtl K.\lnO, ccsctl ‘v/JO f:f;‘s Wtd KCIO. for ClCrsS FE)’ by Kf_lO, /olc#ul

trill O#l fi _ ___ ._.____ -__.- .__... _ ._. _.___. _.__ _._ __ __ ___. _

I ‘f.63.) 5.3GG 0.0055 17.815 7.185 0.0073 13.818 ll.lH;? 0.0x I.)

1o.g.57 1-l 043 o.or43 5.885 rcJ.115 0.0195

--- .__-- - __.- . _ _ _ . _ _ .

I., 008 5.g()L? 0.0083

9.934 ro.oGG 0.0 I40

7.700 12.r91 o.or71

18.343 l-t-G57 O.OZO.(

23.539 lY..)Gl o.o,gG

ClzRlC SULl’llATE _ - -_.. -_ . - _ _ __. _ _._.. _ _. . _ ..-__ .----. .-- _.-.-. -- ___ _ .- _.__._ - - _- ..___-- - _____ _-..___. _. _

CeISW I Nl~‘,l&ES N}ao KAlnO, llSd Nlro b-ES urril le km

w.w&y I

fi ml

/or txe;, f:ES by Cd;O.h

6 _.._ __ ._. . __ _-_-___ _ .^. -. _ . _. - __ --_____ -

o.o8G!, 20.00 14.758 5.242 0.0870 o. 170.5 20.00 0.738 xo.zOr 0.1705

0.~388 20.00 5.630 34.370 0.2388

0 3078 30.00 1 I..)71 18.529 o*3o79 0.3325 40.00 19.982 20.018 0.3325

_-.- . .._ __ ._-__ .._.._ .-. -_._ -- _ - . ..-_ _._--------.--- -. .- . ..-.--__---. ..- -._- -- - .-- . - -.- _... --._ _. -- _

The senior author wishes to acknowledge the help rendered by the junior author, Mr. HARBANS SINGII, B. SC. ; Grad. I.E.E. (London) ; A.M.Inst. E. (London), especially in setting up the apparatus and increasing the accuracy of potentiometric observations.

Rcfcremes p. a92

292 13. SISGII, S. SINGH, H. SINGH VOL. 13 (1955)

SUJEMARY

Ferrous ethylcncdiaminc sulphate has been used as a reducing agent to determine indirectly potassium dichromatc. hyclrogcn pcroxido, potassium permanganate, potassium persulphate, potas- sium chlorate, potassium bromate, and ccric sulphatc by a potontiometric method. An excess of ferrous ethylcncdiaminc sulphatc added to each of the substances in an acid medium is titrated with a standard solution of potassium pcrmanganate, using platinum foil as an oxidation-reduction clectrodc coupled with a saturated calomcl clcctrodc through an agar-agar potassium chloride bridge.

Lc sulfate dc fcr(II) Ithyl&ncdiaminc a GtG utilisG commc rdducteur pour le dosage potcntiomd- triquc iudircct du &hrorn& dc potassium, du peroxyde d’hydrog&ne, d&s pcrmanganatcy pcrsulfate, chlorate et hromatc dc potassium ct du sulfate dc ckium(IV). Un excbs dc sulfate de ferlIIl-bthvl&ne- diamlnc cst ajoutd h &acune tic ccs substances B closer, en solution acitlc. Cet excbs cd&suit6 titrd au nioycn d’une solution &don de permanganate dc potassium, cn utilisant une fcuille de platine commc dlcctrotlc d’oxydo-rbduction, rcliCc a une Glcctrodc au calomel saturdc au moycn d’un pont cl’ngilr-agar-clilorilrc de potassium.

ZUSAMMENFASSUIGG

Das Eiscn(II)Btl~ylencli~minsulfat wurde als recluzicrcndc Substanz verwcndet ftir die intlircktc potcntiomctrische Bestimmung von l~aliumbichromnt, Wasscrstoffsupcroxyd, Kaliumpermanganat Kaliumpcrsulfat, Kaliumchlorat, Kaliumbromat uncl Cerium (IV) Sulfat. Ein Ubcrsclluss von Eiscn (II) Bthylcndiaminsulfnt wircl zu jcder dcr zu bcstimmcndcn Substanzen in eincr saurcn Lijsung gcgcben. Dicscr ubcrschuss wircl clarauf mit Hilfo cincr ICaliumpcrmanganat - Vcrgleicl~sli)suny tltricrt, inclcm man tine Osyclo-reduktions-Platinelcktroclc, cinc gcsiL.ttigte I<alomelclektrodo und tine Rgnr-Agar Brticlcc mlt Kaliumchlorid venvcndct.

1 KAT~IRYN P. CANAWAY AND RALPI~ IX. OESPEIG J. Clrejtr. E:iilc., 24 (1947) 235. 2 B. SING11 AND s. SlXGlr, ad?lfd. C/liUZ. /i&Z, 13 (1955) 221,. a RI(TIIUI~ I. VOGEL, Quahlafivo ~?roq,urnk A ~IUZJWS, Longmans. London, 135r, p. 303.