1698. ------. [INTERNATIONAL HYDROCARBON SYNTHESIS CO.] [Recovering Used Thorium Catalysts.] Italian Patent 374,226, June 16, 1939. Chem. Zentralb., 1940, II, p. 2987.

Catalysts are dissolved in HNO_3, precipitated by Na₂CO₃ solution in such amounts and so slowly at 60° -70° that Co and Ni remain in solution, but the Th(CO₃)₂ is precipitated. The Fe-containing precipitate is dissolved in H₂SO₄, and by addition of solution of K₂SO₄ and Na₂SO₄ the double salt Th (SO₄)₃K₂ is precipitated. This is converted by boiling with a concentrated solution of alkali- or NH₄-carbonate into insoluble basic Th carbonate. The double sulfate can also be treated with excess alkali- or NH₄-carbonate solution so that Th (CO₃)₂ is dissolved, the solution heated, and basic Th carbonate precipitated by means of H₂SO₄ or HCl. The recovered Th is pure enough for making fresh catalysts.