fhree-column volumes of 0.1 N HCl were run through the tube. resin until the eluate was clear and the desired flow rate was obtained. ‘The quantity and mesh size of the resin bed for the experiments differed slightly as indicated in Table l. 3. Elution procedure Tne sample was allowed to pass through the column at a rate of 0,2-0.5 ml per minute and then the column was washed with 20- 60 ml of dilute acid of the same normality as that in which the sample was dissolved. The flow rate was controlled by adjusting the height of a separatory funnel containing the appropriate elut- ing agent. The above fractions contained those ions not adsorbed to the resin and were designated as the anion fractions. The cat- 41ons adsorbed to the resin bed were removed progressively by pass- ing through the column the required volumes of 0.5 per cent oxalic acid, and of 5 per cent citric acid adjusted to pH of 3.5, 4.1, 4.6, 5.1, 6.6 and 6.1 with NH,OH. In some of the experiments a mixture of 0O.15N NH,C1 and 0.1N HCl was used to remove es t3!, Subsequent experiments with spikes have shown the NH,€1-0.1N HCl step to be ineffective and its use has been discontinued. A summary of the elution schedule for each experiment is given in Appendix Table 1. The eluates were collected in cali- brated test tubes in fractions of 2-20 ml, either by hand or by fraction collector, and aliquots of these were used for radioassay. The resin bed was removed from the column at the termina- tion of the elution and was ignited for radioassay. In some of the experiments certain fractions were passed through a second resin column for further separation of the nuclides. amt ; wy at: re 3 JO