was used for the samples taken from near the Columbia River mouth, and a sulphide precipitation method adapted from Sood, Gelden and Velten’ was used for the Christmas where V is the volumeof reagent in ml. and 9 is the salinity of the sample in parts per thousand. This relationship is based on observations in the range of 10-32 per cent. The precipitate was allowed to settle overnight or longer, after which time most of the clear supernate liquid was siphonedoff. The remaining mixture wasfiltered through a Whatman.-42 filter paper under vacuum. The precipitate was wet-ashed with concentrated nitric acid and 30 per cent hydrogen peroxide, dried m a 250-ml. ‘Pyrex’ beaker and counted. The elements present im greatest quantity In sea-water remain in the supernate. This fraction also was dried and counted. The chemical yields by the hydroxide precipitation method for manganese-54, a ee ee ae Island samples. The sulphide method was preferred because it proved to be simpler and equally reliable. Hydroxide precipitation method, Carriers of manganese, cobalt, iron, zine and ehromium (200 mg each) in their chloride form were added to 10 1. offiltered sea-water sample. Under constant stirring. a predetormined amount of concentrated ammonium hydroxide was added dropwise and the precipitate was allowed to settle for 15 min. Then a few more drops of ammoniim hydroxide were added to check the completeness of the precipitation. Tho amount of concentrated ammonium hydroxide required: for complete precipitation of a 10-1. sample varied with the salinity according to the equation: Vi = 100 + 3-78 cobalt-60, iron-59, zinc-65 and chromium-51 ranged from 89 to 100 per cent. Sulphide precipitation method. Carriers of lanthanum, cesium and strontium were added to ‘Millipore’-filtered sea-water samples, with cesium and strontium serving as hold-back carriers. The sample was acidified to dissolve any suspended matter, hoated to 80° C and the pH then adjusted to 11 with ammonium hydroxide. Hydrogen sulphide was bubbled slowly into the solution under constant stirrmg. After the solution had been saturated with hydrogen sulphide, it was taken off the heat and allowed to settle overnight. After scparation from the supernate by filtermg, the precipitate, containing ruth- pe a ne iron, cobalt, zine, nickel, zireonium, ruthenium. cerium, and lanthanum, was placed in an cight-ounce plastic jar and counted. The percentage chemical yields by the sulphide precipitation method for zine-65, cobalt-60, zirconium-95—niobium-95, eerium-144 and ruthenium-103 tags were in agreement with those of Sood eé al.* and ranged from 90 to 97 per cent. Strontium was retained in the supernate, as evidenced by less than 1 per cent 3 a ee ereaes enium, cerium, cobalt, chromium, zine, iron, zirconium