AbstractRecovery and purification of radiochemically useful isotopes, Msh1, MsTh2, ThB and ThC from commercially available aged thorium nitrate were studied by means of ion exchange method. The thorium ion, after having been converted to complex ions by the addition of complex forming reagents such as tartaric acid, citric acid and ethylenediaminetetraacetic acid (EDTA), was not retained by the cation exchange resin column of Dowex 50 in Na‐form when it was allowed to pass through, while its daughter decay products were retained. With the above mentioned organic acids as complex‐forming reagents, the amounts of recovery of the activities were of the following order: tartaric acid>citric acid>EDTA.Using 2NHCl as an eluting solution, MsTh, ThB and ThC were eluted out of the column, but MsTh2was left behind. The latter, however, could be eluted out when 4NHCl was used as eluting solution. When this effluents of 2NHCl was allowed to pass through another resin column of anion exchange resin, Amberlite IRA‐400 in chloride form, ThB and ThC were absorbed, and only MsTh1passed through without retention.Separation of ThB and ThC from each other was carried out by eluting with 8N HCl. By this treatment only ThB was eluted out off the column and ThC was still retained. ThC could be eluted out off the column by means of 2NH2SO4.Using the simple procedure outlined above, the authors succeeded in separating the radioactive decay daughters MsTh1, MsTh2, ThB and ThC from their parent Th232, and from one another. The radiochemical purity of these decay daughters was checked by following their decay curves. These results mere quite satisfa