Chromic Hypophosphite, Cr(H₂PO₂)₃

Chromic Hypophosphite, Cr(H₂PO₂)₃.2H₂O, is obtained by evaporating down on a water-bath a solution of freshly precipitated chromic hydroxide in hypophosphorous acid, washing the green mass obtained with water and drying over sulphuric acid. A basic hypo- phosphite, 2Cr(OH)(H₂PO₂)₂.3H₂O, is obtained as a dark green amorphous fissured mass by the reaction of barium hypophosphite with chromic sulphate and evaporation of the filtrate. When heated to 200° C. it gives off water, and is then insoluble in water and in dilute acids.

Chromium Phosphite is precipitated from aqueous chromic chloride by the addition of an alkali phosphite, heat being necessary for complete precipitation; it is partly separated when phosphorus trichloride, dissolved in water and neutralised with ammonia, is added to chromic chloride, the phosphite remaining in solution giving a green colour to the liquid. When dry, it is a loose grey powder, decomposed by heat with liberation of pure hydrogen.