Chromous Sulphate, CrSO4.7H2O, is produced by dissolving chromous acetate in dilute sulphuric acid, or by interaction of chromium and sulphuric acid. It forms blue crystals, isomorphous with those of FeSO4.7H2O, and is soluble in water, though not in alcohol. It is readily oxidised by the oxygen of the air. Moissan describes a hydrate, CrSO4.H2O, as a white powder, which with water regenerates the heptahydrate.
Several double sulphates of divalent chromium exist: sodium chromous sulphate, Na2SO4.CrSO4.4H2O, is prepared by the action of chromous acetate upon a mixture of sodium sulphate and sulphuric acid. The potassium salt, K2SO4.CrSO4.6H2O, is obtained by alcoholic precipitation of a mixture of chromous chloride and potassium sulphate in solution in absence of air. An ammonium salt, (NH4)2SO4.CrSO4.6H2O, has also been prepared. |