~15- lusteroid test tubes. Oxalate fractions The oxalate fraction of the primary ion-exchange separation of sample P-6 was dried and redissolved in concentrated HCl for the Berar of the transition elements, as described by Kraus and 6 Moore. The sample was passed through a 0.28 cm2 x 26-cm column containing Dowex-1-(200-400 mesh). Determination of strontium-90 Samples of plankton and a sample of shrimp were analyzed for gr90 (5) by the ion-exchange method of Kawabata and Held. The ashed sample was first treated with 80 per cent HNO3 to remove strontium from the bulk of the sample and from most of the other radioisotopes present. The solution containing the strontium nitrate precipitate was filtered through a glass filter and was then dissolved in hot 0.2N HCl. After cooling, it was passed through a cationic resin column and possible contaminants were eluted from the column with 0.5 per cent oxalic acid and 5 per cent ammonium citrate at pH 3.5. . The column was then stored for 14 days to allow the y2 daughter to build up. The Y9° was reeluted from the column with ammonium citrate at pH 3. 5 and the amount of Sr20 present was calculated from the amount of ¥99 recovered. The identity of y90 was confirmed by determining the decay rate of the sample eluted. or actives Mor”