(Reprinted from Nature, Vol. 193, No. 4817, pp. 796-797, February 24, 1962) Occurrence of Bismuth-207 at Eniwetok Atoll Durinc March 18-30, 1961, 308 samples of soil, water, algae, land plants, plankton, fish and invertebrates were collected at Eniwetok Atoll for assay of radioactivity. Two of the samples, taken from the bottom of the lagoon, contained a y-emitting isotope not previously reported at the Eniwetok Test Site. One sample. which consisted primarily of radiolarians, foraminiferans, and small sand grains, was collected in a plankton net placed under the outflow of a salt water supply system for marine aquaria in which the intake pipe was located on the bottom of the lagoon near Eniwetok Island. The other sample was a specimen of a brown alga, Dictyota divaricata Lamouroux. collected in three feet of water in the lagoon off Glenn Island on the west side of the atoll. The algal sample (wet weight 63 gm.) was dried, dry-ashed at 500° C. for 20 hr. (ash-weight 10-6 gm.), dissolved in 500 ml. of 12 N hydrochloric acid to which 20 mgm. of bismuth carrier had been added, and boiled to dryness. Tho y-spectrum of the residue as determined by the use of a 3-in. by 3-in. sodium iodide (thallium) crystal connected to a 256-channel analyser contained the photopeaks of cobalt-57. eobalt-60, zinc-65, manganese-54 and ruthenium-106 —-rhodium-10t. In addition, photopeaks with energies of 0-038, 0-57, 1-064 and 1-77 were present. The latter correspond to the photopeaks of bismuth207. an isotope with a physical half-life of eight years. The presence of bismuth-207 in the algal sample was verified by the following methods. The ash, which had been treated with hydrochloric acid and dried, was dissolved in 50 ml. of 6 N hydrochlorie acid and diluted to 1,000 ml. with distilled water. ‘Dowex 50 W—X8’ resin (50-100 mesh) in the H-form was placed in a glass column (1-4 cm. diameter and 200 em. length). The sample was passed through the column at a flow-rate of 1 ml./min. and the column was rinsed with | litre of 0-2 N hydrochloric acid. The sample eluate and rinse were combinedand dried (anion fraction). The column was eluted with 1 litre of 5 per cent oxalic acid followed by 1 litre of 6 N hydrochlorie acid. The last two fractions were collec- ted and dried separately. 407975 Rh