The construction of a dynamic generator for the separation of carrier-free224Ra is described. The mother228Th was extracted on the top of the column with di-(2-ethylhexyl)phosphoric acid on hydrophobized Chromosorb W DMCS. The function
of the generator was checked during 6 months by measuring the decontamination of224Ra from228Th. Simultaneously the yield of224Ra was determined as a function of the HCl concentration and of the means of milking. The best results were obtained with
0.01–0.1M HCl; the yield was about 75% of the theoretical value, and the224Ra contained less than 0.01% of228Th.