2of Interferences Since the only elements which will precipitate with fuming nitric acid under the conditions used in the procedure are calciun, strontium, barium, radium, and lead, the potential radioactive inter= ferences are radium and its daughters and barium-140 and its lanthanum daughters, Lead and Letho are scavenged in the first yttrium milking end radium and barium are removed in the barium chromate precipitation which immediately follows. In one soil analysis, the precipitate from the first milking was mounted and the activity followed over a period cae aery fa i j of 140 hours. There was a rapid decay initially, then a leveling off to a constant value after two weeks as shown in Figure 1. This indicated the presence of ppele, pp©10 end other shorter-lived radium daughter products, The level of activity after 4.0 hours was about the same as the activity attributed to strontium-90 at equilibrium after the second milkingo Experience has shown that soil containing milligram quantities of titanium, present analytical difficulties which are troublesome but not critical, This element invariably carries through the nitric acid separations, and until it is completely removed in the ‘first milking’, filtrations can be quite difficult and slow, The titanium compound (its chemical form is uncertain but there is evidence to indicate that it is a titanoesilicate complex) does not appear to scavenge significant amounts of strontium. if the prevsaure in the Appendix is strictly adhered to, all interferences are eliminated since a pure strontium fraction is obtained, . ss — .“NAS ~~ ’ =