This procedure permits of the separation by a single precipitation of thorium from relatively large amounts of the lanthanides (Ce, La, Pr, Nd, Sm, Gd) and also from cerium(IV).
The solution (100 mL) should be neutral or faintly acid, and contain not more than 0.1 g Th. Heat the solution to boiling and add slowly and with constant stirring a hot, almost saturated, solution of pure sebacic acid in slight excess. The precipitate is voluminous, but granular, and therefore easily manipulated. Filter off immediately, wash thoroughly with hot water, dry, and ignite (use either a Meker or Fisher burner or an electric muffle furnace at 700-800 °C) in a weighed platinum, porcelain, or silica crucible to constant weight. Weigh as ThO2.