21 Distribution Coefficients—The distribution coeffi- ation iron RPC AR RR. pitartinlecittse «canbe gee had ique1 the Iownitric [ the cont the 107 cients for cesium and rubidium are shown in Figure 14. The distribution coefficients reported for the partition of cesium and rubidum between water and zinc [— ferrocyanide are in agreement with those previously reported by Gorene and Kosta."*) Using nitric acid, the distribution coefficients for 10> E 1.5 with 9 M aeid, and for rubidium from 2520 at zero acid concentration to 1.8 with 9 M acid. The distribution coefficients for rubidium are much lower jo? than those for cesium in dilute acid (up to 4 AZ). At concentrations of acid greater than 4 M, the differ- cya- zinc ences between the distribution coefficients for cesium and rubidium become much smaller, and for 9 Macid, eya- ss of ferated ad; are con‘lons veen NH4NO3 SOLUTIONS HNOs SOLUTIONS cesium range from 9160 at zero acid concentration to are minimal. When ammonium nitrate is used in place of nitric Kd [ to! acid in the aqueous phase, the distribution coefficients for cesium decrease from 9160 to 3.2 at 9 M, and for - cients for the two elements are widely separated at all ammonium nitrate concentrations. 10° L. in the section on methods. The columns were loaded io'L rubidium, from 2520 to 0.9. The distribution coeffi- The Separation of Rubidiwm and Cesium Using Columns of Zinc Ferrocyanide.—Ion exchange columns of zinc ferrocyanide were prepared as described Seeaint tose ends+ with cesium or rubidium by passing 10 ml of water spiked with 7Cs or ®*Rb through the column. The eluant was checked for residual activity, and in all cases greater than 99% of the activity was adsorbed. According to the results presented in Figure 14, a separation of rubidium and cesium should be possible. Rubidium may be eluted first with 2 M ammo- nium nitrate or 3 M nitric acid and then cesium with 9 17 ammonium nitrate or 9 M nitric acid. The results of such experiments are shown in Figures 15 and 16. The rubidium was quantitatively desorbed using either 2 M ammonium nitrate or 3 M nitric acid with little or no contamination due to cesium. While 91% of the cesium was eluted using 9 M nitric acid, only 68% was removed using 9 M ammonium nitrate. Copper Ferrocyanide Distribution Coefficients——The distribution coefficients for the partition of cesium and rubidium between copper ferrocyanide and aqueous solutions of nitric acid or ammonium nitrate are shown in Figure 17. In the nitric acid system, the values of the distribu- Fe, tion coefficients for rubidium show a very noticeable initial decrease from 1590 at zero acid concentration to 34 with 1 M acid, and then continue to drop to a Value of 0.14 with 9 M acid. The value of the distribu- jf i0 | 8 | 6 | 4@ | | 2 0 2 MOLARITY | 4 f 6 jj 8 10 Fic. 14——Distribution coefficients for the partition of cesium and rubidium between zinc ferrocyanide and nitric acid or ammonium nitrate (cf. Figures 17 and 19). tion coefficients for cesium decreases from 38,100 at zero concentration to 5.9 with 8 M acid. Using ammonium nitrate the values of the distribu- tion coefficient for rubidium decrease from 1590 at zero ammonium nitrate concentration to 2.8 with 9 M ammonium nitrate. Similar experiments with cesium give values of Kp which are extremely high, decreasing from 38,100 to 116 with 9 M. The behavior of the copper ferrocyanide prepared in this study was compared to that found for a sam- ple of this exchanger obtained from Folsom. Distribu- tion coefficients for the partition of cesium between ammonium nitrate solutions and the two copper fer- rocyanides were compared. The material prepared for this study gave values of Ky which were twice as large as those obtained using the material prepared by Folsom. This difference will probably be found to be due to variations in the method of preparation and is most likely connected with the concentration of copper in the precipitating solution. Separation of Cestum and Rubidium Using Copper Ferrocyanide—From these values of the distribution coefficient it may be predicted that a good separation