Uranyl Sulphite

The addition of ammonium sulphite to a solution of uranyl nitrate yields a yellow flocculent precipitate to which Muspratt gave the formula UO₂SO₃.3H₂O. It contains, however, some ammonium uranate. A crystalline hydrate, UO₂SO₃.4H₂O, is obtained by evaporating a solution of uranic acid in aqueous sulphurous acid, or by passing sulphur dioxide into an aqueous solution of uranyl nitrate or acetate. It separates in pale green needles, which are insoluble in water but dissolve in aqueous or alcoholic sulphurous acid. When heated to 105° C. it loses seven-eighths of its water. This fact led Kohlschiitter to suggest that it was a complex uranyl compound of composition O(UO₂.SO₃H)₂.7H₂O, but this view is not borne out by conductivity measurements.