Spectrophotometric studies on the interaction of chromic chloride and potassium octacyanomolybdate

.l. Inorg. Nucl. Chem., 1961, VoL 20, pp. 155 to 170. Pergamon Press Ltd. Printed in Northern Ireland

NOTES

Spectrophotometric studies on the interaction of chromic chloride and potassium octacyanomolybdate (Received 19 January 1961; in revisedform 17 May 1961) METALS ions usually react with potassium octacyanomolybdate (IV) to give insoluble complexes, but in a few cases soluble complexes are also formed, such as with Fe(III) and Cr(III), Our investigations are concerned with the formation of the latter complex in solution. Preliminary experimentsO~ showed that the reaction between chromic chloride and potassium molybdocyanide is a slow one. EXPERIMENTAL A solution of potassium octaeyanomolybdate (IV) was prepared by the method recommended by I~ESER~2~ and the strength determined by potentiometric titrations with potassium permanganate solutions. The molybdenum complex was stored in an amber coloured bottle wrapped with black

140

(I)

120

~C)_

I00

c z3

80

B_ o

60

40

\

2O

0

320

I

r

L

i

340

360

380

400

420

Wovefengt h,

1

i

I

440

460

480

500

mza

Fie. l.--Ratio Cr(III) to Mo(CN)s 4- in curve (1) I : 1, (2) 1 : 2, (3) 1 : 3, (4) 2: 1, (5) 3 : 1. Conc of

reactants 2 × 10.8 M. paper. Analar chromic chloride was dissolved in water twice distilled and the strength was determined iodometrically. Mixtures of solutions of chromic chloride and potassium molybdocyanide were placed in a 50°C (thermostat) water-bath for 2½ hours to ensure complete reaction; their optical (1) W. U. MALIK and S~ IF'nKIIAR ALI, Naturwiss 20, 579 (1959). c2} L. F. FIESER,J. Amer. Chem. Soc. 53, 5226 (1930). 155

156

Notes

80

70

60

50

4o

o x

~5

20<

10

0 0.l

I 0.2

T

I

~

I

I

I

0.5

0.4

0'5

0-6

0.7

0"8

0"9

FIG. 2 . - - R a t i o [Cra+]/{[Cra+] 4- [ M o ( C N ) a 4 - ] } . Original conc o f reactants, ( I ) 2 X 10-2 M , (2) 1 x I0 - 2 M , ( 3 ) 5 X 10- a M . F i n a l conc ranges f r o m l X 10- 4 M t o 9 X 10- ~ M . O . D .

for (2) and (3) is shifted by 1 and 2 cm respectively.

70

60 cd O >, E, c

o

3

50

40

5O

20~

IC 0.1

I 0"2

L 0-3

I 0.4

I 0.5

! 0 6

I 0"7

L

0.8

0.9

FIG. 3.--Ratio [Cr3+]/{[Cra+] -F [Mo(CN)a4-]}. Conc of reactants (1) I X 10-a M, (2) 1.25 x 10 -a M .

Notes

157

densities in 1 cm Corex cells were measured with a D U spectrophotometer with photomultiplier attachment. The maximum absorption for all the mixtures was found at 365 m/~, indicating the formation of only one complex ts~ (Fig. 1). The composition of this complex ion was determined by JoB's methodC4, ~ of continuous variation and the slope ratio method, ce~ For the method of continuous variation three sets of mixtures were prepared as above with reactants at concentrations of 2 × 10-3 M, 1 × 10 -3 M and 5 x 10-a M and optical density at 365 m/~ was measured, after dilution to a concentration of 10-3 M. The absorption of chromic chloride and potassium molybdocyanide at 10-8 M was also determined at 365 m/~, the former being negligible. The difference between the O.D. of the mixtures and that of potassium molybdocyanide was plotted against the ratio [Cr3+]/[Cr3+] + [Mo(CN)84-]; (Fig. 2). For the slope ratio method the concentration of potassium molybdocyanide was kept constant and the concentration of chromic chloride varied, the ratio of the slopes over the straight line portion of the curves determined. DISCUSSION The combining ratio as indicated by JoB's method and the slope ratio method is 1 : 1 ; the composition of the complex can therefore be given as KCr m Mo~V(CN),. I f two concentrations (a~ + b 0 and (a2 + b2) of the reactants have the same O.D. (that is the same value of x, the concentration of the complex), then the equilibrium const, t~ k

x

x

(al -- x)(bl -- x)

(az -- x)(b2 -- x)

alba or

x

-

-

a2b~

(ax + b~) -- (as + bz)

For two mixtures having the same optical density (0.40), the value o f x was found to be 2.67 × 10-4 M; the equilibrium constant was estimated to be 4.21 × 104 (Fig. 3). Acknowledgement--Thanks are due to Dr. AKHLAQR. KIDWAI, Head of the Department of Chemistry, Aligarh Muslim University for his interest during the progress of the work. WAHID U. MALIK Chemical Laboratories S. IFTIKHAR ALI Muslim University Ali~arh, U.P., India

~a) W. C. VOSBURG~Iand G. R. COOPER, J. Amer. Chem. Soe. 63, 437 (1941). ~4) p. JoB, Ann. Chim. 9 (10), 113 (1928). ~ P. JOB, Ann. Chim. 6 (11), 97 (1936). is) E. HARVEYand D. L. MANNING,d. Amer. Chem. Soc. 72, 4488 (1950). (7~ A. K. MUKHERJIand A. K. DEY, Proc. Natl. Acad. Sci. India 26, 20 (1957).

Half-lives of 117In and 11Train (Received 2 March 1961 ; in revised f o r m 2 M a y 1961)

THE half-life of 11qn has been reported to be 70 min by CORYELLtlj and 1"1 hours by McGrr~ms. t~ In studying the reaction xlsIn(~t,2p)~TIn, we have observed a half-life of ,~40 min which could not reasonably be assigned to any nuclide other than Xlqn. It thus appeared necessary to check the literature values, tL2~ We have essentially repeated McGrN~as' experiment, t2~ Cadmium metal was bombarded for about 20 min with a 2 0 / t a beam of 14-MeV a n d 5-MeV deuterons in separate irradiations at the Massachusetts Institute of Technology cyclotron. The major cadmium activities formed in the (d,p) reaction are 43-day x~'~Cd, 54-hr 115Cd, 3-hr nT'~Cd, and 50min 1~7Cd. The decay of xxs'~Cd is to the ground state of llSIn, while m C d feeds the 4.5-hr Xlb'~In t~ C. D. CORYELL, P. LEVEQUEand H. G. I~dCHTER,Phys. Rev. 89, 903 (1953). I~ C. C. MCGINNlS, Phys. Rev. 97, 93 (1955).