Step 4. Evaporate filtrate to 2 ml. Add 25 ml of zine uranyl acetate reagent (see Note 3). Allowto digest with intermittent stirring for 4 to 5 min. Filter. Wash 5 times with small portion of sinc uranyl acetate, Wash twice with 2 to 3 ml of ethyl alcohol (see Note 3). Use 2 to 3 ml of hot dil. HCl to wash the precipitate into a 50-mul centrifuge tube. Cool in ice bath. Add 5 mg Ce* + 5 mg K*. Step 5. Then add 15 ml of zinc uranyl acetate reagent for 15 min, Centrifuge, and discard supernatant. Wasb precipitate 2 times with 5 a] of n-propyl alcohol. After washing, slurry precipitate in 10 mi of n-propyl] alcohol and precipitate NaCl with BC1 gas (see Kote 4). . Filter on a weighed filter paper disc in a small filter tower, and wash 3 tines with 5 ml of n-propyl alcohol. Dry the precipitate at 110°C for 10 min, weigh as NaCl, and mount on a counting disc. 4.2.1 Notes 1. Unless otherwise noted, all solutions are to be kept in an ice bath during the entire procedure, 2. It my be necessary to repeat the centrifugation 2 to 3 times to assure complete precipitation of cesium and silica, 3. Z4dno uranyl acetate reagent was saturated with sodium zinc uranyl acetate; n-propyl alcohol was saturated with NaCl; ethyl alcohol was saturated with sodium sinc uranyl acetate. filtered into a fresh container before using. 4. A.3 These solutions were Gas flow was continued for 10 min. SEP. ION OF POT. CT Potassium is first separated with the alkali metal fraction obtained from 0.5N-HCl elution of the cation resin colum (see socium pro- cedure). (10 Purification is then accomplished by the following prccedure,. Step mg/ml), 1. To 2 ml of the alkali metal fraction add 1 ml of Ca’ ml of K* (10 mg/ml) and 10 al of 6N-HCl in a 50-ml centri- fuge tube, Add 0.5 ml of 0.13 M silicowolframic acid and allow to stand with occasional stirring for 5 min. Centrifuge and wash precipitate twice with 5 ml of 6N-HC1. In a 100-ml beaker combine washes with supernatant and discard precipitate. Add 2 drops of silicowolframic acid. If precipitate forms repeat centrifugation and washes. Repeat until the formation of a precipitate is no longer observed. Step 2. On a hot plate evaporate solution to dryness. Cool and then add approximately 5 ml of 10 per cent HCl solution. Break up lumps of silica with a stirring rod. tube and centrifuge, HCl solution. Transfer solution to a 50-ml centrifuge Wash residue three times with 2 ml of 10 per cent Svaporate combined centrifugate and washings by swirling over a burner until the volume is approximately 3 ml, Cool for 2 min, Step 3. Carefully add 5 ml of 70 per cent HCl0,. Evaporate by swirling over a burner until dense fumes of HC10, are evolved, Cool for 5 min in air, then place in un ice bath, To the cold solution add 15 ml of absolute ethanol. Step4. Filter on a weighed filter paper disc in a emall filter 137