-ll- D Results The identification of the isotopes in the present samples was confirmed for both the chemical and ion-exchange resin col- umn methods by the use of radioactive spikes. In the latter technique the spikes were used to determine accurately the elu- tion pattern under the conditions of the present work. Regard- less of the number of isotopes used in an experiment, the elution pattern remained essentially the same; the isotopes were always eluted in the same fraction as shown in Table 2, Table 2. Summary of the lsotopes eluted from Dowex 50 cationexchange resin Preetion Isotopes present Anions Rut OO_gp,t °F Zr? -Nb?? 0.5% Oxalic Acia 0.15 N NH,Cl+ O.1 N HCl Zr? -Nb?? Pe? gr??-Nb?5 Csi3? 5% Ammonium Citrate pH 3.5 a-c ¢3t37 celt4_prl 44 Zn05 d-e zn05 f-j mn54 pH 4.1 a-e mn54 f-h pH 4.6 C00 gr90 sr?? a U7