or time. ese original attempts to determine strontium-90 in soil, Yor faliout documentation at least, were not always successful and it is unfortunate that so many samples were analyzed using incompletely developed methods. There has been wide disagreement in results reported for 2 single sample among several different laboratories. Before any past soil data is used, one should be aware of the extraction method employed. It is the purpose here to present a procedure which has been Severely tested and the reproducibility and reliability of which has been established. It has been shown that other extraction methods remove less strontium-90 from soil than can be leached with 6 normal hydrochloric acid. In addition, the direct milking techniques used at one time by several Isboratories (223) preclude the possibility of obtaining a pure strontium fraction and thereby evaluating the strontium yleld for each sample. Furthermore, assay of the initial activity due to yttrium-90 milked from the impw's strontium-90 » requires extrapolation of a decay curve which may represent contaminating activities due to Ac@28 | pel, and Pr“1t9, these disadvantages could easily Jead to anomalous and unreproducible results. | The procedure used at HASL involves the eventual separation of & pure strontium fraction which, when milked at equilibrium, yields an yttrium daughter activity which may be positively identified as yttrium-90 by half-life and beta absorption measurements. (2) There is a loss of Martell, E.A., The Chicago Sunshine Method, The University of Chicego, AECU=3262. . (3) Kulp, J. L., Ecklemann, W. Re, Schulert, A. R., Lamont Sunshine Coemical Procedures. ~-2. + 6 ae mm os : = 4 MA RAS OSS ate SRA - Te . * SETAE ATTeMt aiEE ete ae aI Psae