~e the procedure developed by Swartout et al. (1944) and Tompkins et al. (1947) of the Manhattan Project. This procedure employs the selective adsorption on, and elution from, an lon-exchange column with the aid of certain organic acids which serve as spe- cific complexing agents for individual ionic species. This tech- nique was used by Swartout, Tompkins and others at the Clinton Laboratories, Oak Ridge, to separate and purify fission product species in curie and trace amounts, and again by Kimura etal. (1956), Takanobu et al. (1956), and Ishibashi et al. (1956) to separate and identify the individual fission products in various biological and non-biological samples collected in the vicinity of Bikini Atoll and in Japan. 1. Preparation of the samples Samples of ash weighing from 108 to 2,568 mg were wet ashed under the conditions given in Table 1, evaporated to dryness and redissolved in 0.1 N or 0.2 N HCl. The sample was filtered and an aliquot was removed for radioassay. The filtrate was then passed through an ion-exchange column which was prepared in the following way. 2. Preparation of the resin column Dowex 50*, a sulfonated polystyrene resin of the cationic type, supplied in the H-form was washed three times with a greater volume of 1-6N HCl, rinsed twice with distilled water and twice with dilute HCl. The resin suspension was added to a glass column containing a glass wool plug in a constriction at the base of the * Dow Chemical Co., Midland, Michigan