. 78, rss, aAIX= . of “on ace alage WEX 0) and stilyand eXive ‘he for enlu- ted ion um as ese AW pe TOPE ARONAAN it ART oA 158). logy 155). counted using a 3”-x-2” Nal (Tl) crystal. The counts of the ferrocyanide was allowed to digest for one to two hours in a boiling water bath, and after cooling to trum was accumulated on a 400-channel pulse height nitrate while stirring. The resulting fine precipitate "roc. eal. cyanide were added dropwise to 2500 ml of 0.1 Mf zinc room temperature, was filtered through a sintered glass funnel. The precipitate was washed with ammonium nitrate, then distilled water, and dried at 110° C for 4 hr. The resulting solid was ground in a mortar, the fraction between 40 and 200 mesh being collected. Copper and nickel ferrocyanides were prepared in a similar manner using 167 ml of 0.1 JZ potassium ferrocyanide and 500 ml of 0.1 Af copperor nickel nitrate. Samples of copper and zirconium ferrocyanides (less than 0.25-» mesh) were also obtained from T. R. Folsom at the Scripps Institute of Oceanography for investigation. Cesium-137 was obtained from an JAEA standard ecsium solution containing 25.79 »Ci/ml. The con10-* M. of cesium was approximately 7.3 X Rubidium-86 was prepared by irradiating 10 mg of spectrographic grade rubidium chloride* in the Jug- gernaut reactor. After irradiation, the material was dissolved in 7 mi of water so that the rubidium con- centration was 1.2 x 107? M. Determination of Distribution Coefficients (Kp) Distribution coefficients for copper, zinc, and zirconium ferrocyanides were measured in the followmg manner. One-tenth gram aliquot portions of the in- organic ion exchanger were weighed into two dram (7 ml) polyethylene flip-top vials (Olympic Plastics). Five milliliters of the required aqueous phase were added, followed by a 50-y1 aliquot of the radioactive nuclide (387Cs or ®®Rb). Blanks were prepared to measure the total activity added to the vials by following the same procedure, only omitting the exchanger. If the Kp was known to be very large, smaller amounts of the exchanger were taken. The maximum concentrations of rubidium and cesium in the final solution used were 1.4 x 10-4 M and <10-7 M, respectively. The vials were shaken overnight on a rotary shaker. The two phases were then allowed to separate, and the supernatant aqueous phase was filtered through 0.45- or 0.8-» Millipore filters. Four milli- liters of the filtrate were pipetted and made up to 5 ™ml with distilled water into 2-dram polyethyleneflip- top vials. These samples, as well as the blanks, were _— * Obtained from Johnson Matthey Company. analyzer. The counts per gram of exchanger were calculated from the difference between the total counts in the aqueous phase after equilibration and the total activity added initially. The distribution coefficients for the tracer between the inorganic ion exchanger and the aqueous phase were calculated from Kp => counts/g of exchanger counts/ml of aqueous phase ~ Kinetics of Attainment of Equilibrium The rate of attainment of equilibrium of the ion exchanger with the cesium ions was determined by measuring the apparent distribution coefficient after different times of shaking. Solutions of Radioactive Nuclides centration were recorded on a scaler, and the gamma-ray spec- Stabiluty of the Inorganic Ion Exchangers A procedure similar to that used for the measure- ment of the distribution coefficients was employed to determine the stability of zine and ferrocyanides in strong acid, except that no radioactivity was added. The aqueous phases were subjected to analysis by atomic absorption spectroscopy for iron and zine. The techniques used were as described in the PerkinElmer 303 atomic absorption spectrophotometer manual for these two elements. Column Expervments A water slurry of the exchangers was prepared so the fines could be decanted. Ion exchange columns were made by packing a 7-cm length of polyethylene tubing, 0.6 em diameter, with about 3 em of the slurry under gravity. Ten milliliters of water were spiked with a known concentration of cesium, rubid- jum, or both, and passed through the column at a constant rate of 1 ml/min by means of a polystaltic pump. The eluate from the column wascollected and counted to check the efficiency of adsorption of the cesium or rubidium. Then, 10 ml of a selected eluent were passed through the column at a rate of 1 ml/ min. Fifty-drop fractions (1.5 ml) were collected and then counted. The columns were regenerated by pass- ing water through them. RESULTS AND DISCUSSION The ion exchange properties of the ferrocyanides of zinc, copper, and zirconium have been investigated in this study. Distribution coefficients were measured for the partition of cesium and rubidium between several different solutes and these ferrocyanides. The stabil-