v in the precipitate. As in the otassium and cesium remained in the bulk of the sea salts and no wation was made. » supernate from the foregoing pro. hydrogen sulphide was driven off was adjusted to 5 with ammonium acid. Strontium was co-precipitated xalate using ammonium oxalate. The (100-200 mesh). When the yttrium- the resin bed the citrate mass was acid (0-2 N nitric acid) wash. The ped off the column with about 5 ml. .0 @ Stainless steel planchet, dried and ree residue counted. This strontiumoted from a procedure developed by 4 determined in the sea-water from »y this method and also by the method and Katsuragi®. Tn tho latter method ation of calcium and strontium is EDTA-masking of calcium and 90 as yttrium hydroxide after secular cd. he method of extracting phosphorusas suggested by the work of Proctor why and Riley’. Sea-wator was placed iel and allowed to react with a comning ammonium molybdate, sulphuric and potassium antimony tartrate’. vutanol were added to 150 parts of tion was made more acidic to favour tybdenum blue. After extraction the wkwashed with dilute sulphuric acid heat. The residue was dissolved in a 4 Mouth of Columbia River N’inj Average Maximum WJN'/nt 10/25 15/25 150 21 Christmas Island * Average Maximum 770 350 November 1961-June 1962 oy cid to remove any unadsorbed connt oxalie acid was added to remove mn was stripped off yttrium-90 as iplex with 5 per cent ammonium torage time for 2 weeks was allowed iibriam between strontium-90 and stablished. The column then was imum volume of ammonium citrate. o break up the yttrium citrate comg solution was passed on to a shortcolumn containing a 2-em resin bed Radionuclide Cr on ring, was wet-ashed with nitric acid After rinsing with RADIONUCLIDES IN FILTERED SURFACE SEA-WATER FROM TWO AREAS OF THE PACIFIC OCEAN (VALUES IN pe./I.) January—September 1961 side. The ash residue was re-prent nitric acid to reduce the calcium— 1e strontium nitrate thus obtained N hydrochloric acid and the resulting on to a ‘Dowex 50W X-8’ (100-200 resin column. Table 1. 580 May-July 1962 siCr 719 1,300 SZn 8/9 51 12 4/24 ZrOND 7/9 4-5 16 11/24 ORG 5/9 0-79 MLIMCe 9/9 94 2-5 27 4/24 13/24 1:3 16 3-7 10 BCS 8/24 0-62 “Co 2/24 0-38 13 71 32 46 11 7-0 * Fromref. 1. + N’in, Namber of samples with radioactivity greater than background plus the 95 per cent counting error/No. of samples analysed. minimum amount of aqua regia and again evaporated to dryness. The residue was dissolved in 50 ml. of 15 per cent hydrogen peroxide and made up to 2 N in hydrochloric acid. This mixture was added to a scoparatory funnel and the molybdate extracted with an equal volume of tri-butyl phosphate. The organic layer was discarded and the aqueous layer extracted again with an equal volume of tri-butyl phosphate. The aqueous layer was then dried on a stecl planchet and counted for phosphorus32. (A more complete description of the method will be reported by Chakravarti, Tuell and Larson®.) Counting systems. Tho y-counting system included a 3-in. solid erystal of sodium iodide, thallium activated, used in conjunction with a 512-Nuclear Data 120 analyser with an X--¥Y recorder and a digital print-out. Caleulations were carricd out on an IBM 709 digital computer programmed to analyse for nine isotopes and to express results in picocuries (uuze.) per g or per |. at time of eollection. Only values which were greater than the background plus the 95 per cent counting error were considered signifieant: all other values were considered to be zero. Two types of low-background Geiger-Miller counters were used, one for yttrium-90, another for phosphorus-32. The systems included sufficient massive shielding and cosmic-ray guard tubes to reduce the background to approximately 1-5 and 1-0 counts per min. respectively. The counting efficiencies were approximately 25 per cent for vttrium-90 and 40 per eent for phosphorus-32. All counts wore standardized and the results aro expressed in picocuries per litre (pe./l.) at the timeof collection. The average and maximum values of radionuclides, except those of strontium-90. potassium-40 and phosphorus-32, in sea-water samples are given in Table 1. This Table is a summary of the results of analyses of ~ 2