strontium-85 activity in the precipitate. As in the hydroxide method, potassium and cesium remained in the supernate with the bulk of the sea salts and no further chemical separation was made. Strontium-90. The supernate from the foregoing procedure was acidified, hydrogen sulphide was driven off by heat and the pH was adjusted to 5 with ammonium hydroxide and acetic acid. Strontium was co-precipitated with calcium as the oxalate using ammonium oxalate. The precipitate, after filtering, was wet-ashed with nitric acid and hydrogen peroxide. The ash residue was re-precipitated in 80 per cent nitric acid to reduce the calcium— strontium ratio. The strontium nitrate thus obtained was dissolved in 0:2 N hydrochloric acid and the resulting solution was passed on to a ‘Dowex 501W X-8’ (100-200 mesh) ion-exchange resin column. After rinsing with 0-2 N hydrochloric acid to remove any unadsorbed contaminants, 0-5 per cent oxalic acid was added to remove radioiron. The cohunn was stripped off yttrium-90 as yttrium citrate complex with 5 per cent ammonium citrate at pH 3-5. Storage time for 2 weeks was allowed for the secular equilibrium between strontium-90 and yttrium-90 to be established. The column then was ro-eluted with a minimum volume of ammoniuin citrate. the eluate acidified to break up the yttrium citrate complex and the resulting solution was passed on to a shortstemmed eyedropper column containing a 2-cm resin bed of ‘Dowex 501V X-8’ (100-200 mesh). When the yttrium- 90 was adsorbed to the resin bed the citrate mass was removed with dilute acid (0-2 N nitric acid) wash. The yttrium-90 was stripped off the column with about 5 ml. of 6 N nitric acid on to a stainless steel planchet, dried and the relatively mass-free residue counted. This strontium90 method was adapted from a procedure developed by Kawabata and Held!. Strontium-90 was determined in the sea-water from off the Oregon coast bythis method and also by the method of Mivake, Saruhashi and Katsuragi®. In the latter method an oxalate precipitation of calcium and strontium is used, followed by EDTA-masking of calcium and recovery of yttrium-90 as yttrium hvdroxide after secular equilibrium is reached. Phosphorus-32. The method of extracting phosphorus32 from sea-water was suggested by the work of Proctor and Hood‘ and Murphyand Riley’. Sea-water was placed in @ separatory funnel and allowed to react with a composite reagent containing ammonium molybdate, sulphuric acid, ascorbic acid and potassium antimony tartrate’. Seven parts of N-butanol were added to 150 parts of sample, and the solution was made moreacidic to favour extraction of the molybdenum blue. After extraction the organic layer was backwashed with dilute sulphuric acid and dried under low heat. The residue was dissolved in a 4