t3 Tue decay of “cs milked yttoium-90 has been followed for every sample analyzed and within two standard deviations due to the error in counting, e, straight lins representing the established half-life (64.4 hours)? is always found. Figure 2 shows seven examples of the decay curves obtained. In several cases waere the activity has been sufficiently high, the yttrium-90 fraction has been analyzed by the beta absorption method of Harley and Haliden.‘?) The value for the energy found by this method agreed satisfactorily with that generally accepted (2.26 Mey). (5) 2.8 Compaxison of Extraction Method and Fusion By fusing an aliquot (1 lb.) of soil with sodium carbonate at temperatures eround 200° o(9) and then dissolving the melt in mineral acid, one can solubilize the soll campletely. If the assumption is made that the fusion analysis gives the total amount of strontium-90 in the soil, one can express the fraction or percentage of the total amount of strontium-90 removed by the hydrochloric acid extraction. The soil sempiss shown in Table 5 were collected in pasture areas in the United States in 1956 and 1958. At least ten reanalyses have been carrisd out on each sample, (1°) The values for a/m sr”? per kg soil ars averag:s and the error term is one standard deviation from the mean. (6) Volchok, H. Ley Kulp, J. Ley Phys. Rev. 97, 102 (1955). (7) Harley, J. H., and Hallden, N: A., Nucleonics, Jan. 1955, P. 32. (8) Johnson, 0. E., Johnson, R. G., langer, L. M., Phys. Rev. 98, 1517 (1955). (9) This work vas done at the USDA Iaboratories at Beltsville, Md. -under tne dizvecricnu of Br. L. T. Alexander. (10) See proceturs given in NYO-4700 - Manual of Standard Procedures. ~ Vk . } ne a he 7S ‘ & “ » *” 3 aS MRL 4 ESS = Say Sag Te RTT LS FR Aces / ~ _ =& ~*~ Ms a Se = es. . ~ NS st & S ~—s Say sags _ ae TS, “. Se = Tey. : a aA ee ermeeeim 8 eee ET ee LE Te. = “ay ™ oh : ~, ey my,Be =a ™~ = = RReR aera oe = “Na =. . ~ * a ss E “S Sa Saye a