PATENTS

3134.----- [RUHRCHEMIE, A. G.]  [Process for Recovering Thorium.]  German Patent 745,859, Dec. 6, 1944; appl. R 103,605, R 413, filed Oct. 22, 1938 (Cl. IV b-12 m).  TOM Reel 37, bag 3,451, item 35, 6 pp.; Meyer Transl. PC-S-II, Fischer-Tropsch, vol. 4, chap. 136, 1949, p. 24.

The bircarbonate obtained by the method of German Patent 745,557 (abs. 3133) still contains 0.3-0.5 parts of Fe₂O₃ per 100 parts ThO₂.  It has now been found that if the K₄Th (SO₄)₃ still containing a little Fe is treated with an excess of alkali carbonate solution until the Th bircarbonate first precipitated is redissolved, the alkali Th double carbonate solution is freed of the last traces of Fe by eating and subsequent filtration.  The Th double carbonate solution, which has been freed of Fe, is decomposed with H₂SO4 and the sulfate solution separated from the precipitated Th bicarbonate is again used for treating fresh Fe-Th sludge.  By decomposing the above double carbonate solution with  HCl and cooling the solution from which the precipitated Th bircarbonate has been filtered, the resulting alkali sulfate crystallizing out is used for treating fresh Th-Fe sludge.  Flowsheets are shown.