Zirconium Sulphates

Anhydrous zirconium sulphate, Zr(SO₄)₂, is obtained by dissolving the hydrated oxide in concentrated sulphuric acid, evaporating, and carefully igniting the residue. Too strong ignition decomposes the salt and converts it into oxide. The anhydrous sulphate dissolves in much water with great evolution of heat owing to the formation of the hydrate Zr(SO₄)₂.4H₂O, which separates in rhombic crystals from a solution containing sulphuric acid. From a dilute solution the basic salt 4ZrO₂.3SO₃.15H₂O gradually separates, and is sufficiently definite in composition for atomic weight determination; whilst from a concentrated solution near the boiling-point the salt 2ZrO₂.3SO₃.5H₂O crystallises. The precipitate formed by adding alcohol to zirconium sulphate solution varies with temperature and concentration. From strongly acid solutions the acid salt Zr(SO₄)₂.H₂SO₄.3H₂O separates in prisms which deliquesce in air, forming Zr(SO₄)₂.4H₂O; the monohydrate Zr(SO₄)₂.H₂SO₄.H₂O is also known.

Ruer has observed that a solution of normal zirconium sulphate does not give the same reactions with oxalic acid and ammonium oxalate that a solution of the chloride gives. He therefore assumes that this solution contains zirconium in a complex anion, thus H₂(ZrOSO₄.SO₄), to which complex sodium and ammonium salts M'₂(ZrOSO₄.SO₄) correspond. The constitution of hydrated crystallised zirconium sulphate is accordingly represented thus: ZrOSO₄.H₂SO₄.3H₂O. This view is not accepted by Hauser; but Rosenheim and Frank write the formula in question ZrO(SO₄H)₂.3H₂O, thus representing it as zirconylsulphuric acid; and, moreover, have obtained the following complex sulphates:

Zr₂O₃(SO₄K)₂.8H₂O, Zr₂O₃(SO₄Rb)₂.15H₂O, Zr₂O₃(SO₄Cs)₂.11H₂O, as well as Zr(SO₄K)₄.3H₂O and Zr(SO₄Na)₄.4H₂O.