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