i strontium-90 in the procedure as the separation involves a number of steps, and consequently it is necessary to correct for yield. This vield correction varies from one soil type to another, but if the samole contains negligible amounts of stable strontium, the weight of strontium carbonate recovered from the added carrier strontium, is a good measure of the recovery. However, in those cases where the stable strontium is appreciable, the yield correction must be determined using strontium-85 tracer. This isotope is a pure gamma emitter and with sufficient washing and reprecipie tation, does not interfere with the measurement of yttrium-90 beta activity. It is possible to estimate the leached stable strontium by the simultaneous use of both recovery techniques. If this is to be done, of strontium from calcium must be effected, j complete separation On the other hand, if a measure of the extracted stable strontium is not desired, the tracer can be used to determine the strontium yield even when calcium has not been completely | separated. It is important to realize that no strict procedure can be | written for soil samples in general as soils differ markedly from one location to another, This is not only true with regard to the relative proportions of stable elements but also for the natural radioactivity which is always present. The procedure described in this report is not intended to be specific with regard to the number of fuming nitric acid separations necessary, for example, or volume conditions, These must be determined iit by the analyst for each separate sample. * - ~. eOE AL 7 & a . “NAS e : : 7 : . Ce . Ska OS, ~ RA oo