Complex Thorium Sulphates

Thorium sulphate unites with the sulphates of the alkali metals to form various complex sulphates. Berzelius appears to have obtained the salt K₄Th(SO₄)₄.2H₂O by mixing solutions of the constituent sulphates; but Rosenheim, Samter, and Davidsohn state that the anhydrous salt K₄Th(SO₄)₄ separates when the solutions are mixed; whilst the following sulphates have been obtained by Barre: Th(SO₄)₂.K₂SO₄.4H₂O; Th(SO₄)₂.2K₂SO₄.2H₂O; 2Th(SO₄)₂.7K₂SO₄. From mixed solutions of sodium and thorium sulphates the two salts Na₂Th(SO₄)₃.12H₂O and Na₂Th(SO₄)₃.4H₂O have been prepared, and from ammonium and thorium sulphates the salts

(NH₄)₂Th(SO₄)₃.4H₂O; (NH₄)₆Th(SO₄)₅.3H₂O; (NH₄)₄Th(SO₄)₄.2H₂O; (NH₄)₈Th(SO₄)₆.2H₂O.

The rubidium and caesium salts Rb₂Th(SO₄)₃.2H₂O and Cs₂Th(SO₄)₃.2H₂O have also been prepared.

The double potassium sulphates are slightly soluble in water, but insoluble in a saturated solution of potassium sulphate; the double sodium (and ammonium) salts, on the other hand, are fairly soluble in saturated sodium (and ammonium) sulphate (e.g. about 4 parts of Na₂Th(SO₄) 3.6H₂O per 100 of solution at the ordinary temperature).