ATE EE Sa oe die ae at a
20
zinc and iron found in the solute after equilibratic
100
for 16 hr.
90/-
Table 5 shows the concentration of zine and irc
found in solution after 1 g of zine ferrocyanide h¢
been equilibrated with 1 ml of the appropriate aqu
ous phase. The average concentrations of iron in tl
80;70/r-
nitric acid solutions were approximately equal. Hov
ever, the concentration of dissolved zinc in the nitr
acid solutions was ten times the concentration of tl
iron, while for ammonium nitrate solutions, the coi
centration was fourtimes as great. Assuming thatt]
molecular formula of the precipitated zine ferrocy.
nide is ZneFe(CN)., then the concentration of zn
should be twice that of the iron. The zine ferrocy.
nide was originally precipitated using a 50% excess
Ky
zine in order to aid complete precipitation of the fe
rocyanide. It is highly probable that the precipitat
material would accumulate excess zinc ions by a:
sorption or occlusion and that it is these ions that a.
being preferentially dissolved. The even greater con
centration of zine in solution under acid conditio:
20K
may be due also to a competitive reaction betwee
zinc and hydrogen ions.
10
o
|
2
|
4
1
6
l
&
|
10
|
[2
i
4
|
I6
tJ
I6
|
20
oe
22
oe
24 26
28
HOURS
Fic, 13.—Rate of attainment of equilibrium in the partition
of cesium between zine ferrocyanide and nitric acid.
ity in strong acid and the rate of attainment of exchange equilibrium of the zine ferrocyanide were also
determined. The results obtained will be discussed
separately for each of these inorganic ion exchange
materials.
Zine Ferrocyanide
Rate of Attainment of Ion Exchange Equilibrium.—
The rate of attainment of equilibrium for the partition of cestum between zinc ferrocyanide and 4 M
nitric acid was determined. The results are shown in
Figure 13. The value of the distribution coefficient
TABLE 5 ConcentTrRaTIONs OF IRON AND ZINC IN VARIO
SOLUTIONS AFTER 1 G oF ZINC FERROCYANIDE Has BEE:
EQUILIBRATED WITH 1 ML OF THE APPROPRIATE
AQUEOUS PHASE
Molarity
probably due either to surface decomposition of the
inorganic exchange material by the acid or to a com-
petitive reaction with the hydrogen ions from the
acid.
Stabihity of Zine Ferrocyanide-—In order to deter-
mine the stability of the zine ferrocyanide in the presence of various eluants likely to be employed in the
separation of rubidium and cesium, a series of experiments was set up to determine the concentrations of
NH,NO;,g/ml
Concentration of zinc
1
2
3
4
5
6
7
‘8
9
Average
Molarity
(Kp) increases to a maximum after shaking for 45
min and then decreases slowly thereafter with longer
equilibration times. The decrease at longer times is
HNO, g/ml
2.2 x 107?
1.75 xX 10°?
1.69 x 10-?
1.72 x 107?
8.9
8.9
8.3
9.9
8.3
9.1
8.8
8.6
8.6
1.88 * 107?
8.9 * 1073
1.75 x 107?
1.95 xX 107?
2.1 * 107?
1.44 x 107° M
*
x
K
x
x
«
X
x
x
10-°
10°?
10°
10°
10°
107%
1073
10-3
107%
6.8 « 10-2 MW
Concentration of tran
1
2
3
5
6
7
8
9
Average
Molarity
2.9 * 1073
1.7 < 10°
9.5 * 10-4
2.1x 10%
4.2 x 10°3
3.1 *& 10°?
1.7 x 10°
2.1 * 10°
2.9
7.4
1.8
1.7
X
xX
x
X
1073
10°
1073
1073
2.3 % 107%
4.1 10°? M
2.0 x 10°
3.6 x 102° M