Precipitated cuprous oxide [Cu2O] is acted on rapidly by phosphine at ordinary temperature, forming a grey white mass and water, the grey substance is
quite insoluble in water, if air be excluded; it is [PCu3]. It melts at a red heat, is rapidly dissolved by nitric acid or bromine water, and is
attacked by hot sulfuric acid, with the formation of sulfur dioxide and phosphine. It does not reduce potassium permanganate.
While phosphine acts differently on the aqueous solutions of different cupric salts, its action of the ammoniacal solutions of all of them (chloride,
sulfate, nitrate, acetate, formate, hydroxide) is the same. Copper phosphide is formed in amount corresponding to two-thirds of the phosphine which
disappears, while the phopshorous of the other third is founf in the liquid, as phosphoruc and hypophosphorous acids in molecular proportions-
(6)PH3 + (12)CuCl2 + (6)H2O + (x)NH3 --> (4)PCu3 + PO4H3 + PO2H3 + (24)HCl + (x)NH3
If, after the absorption of the phosphine, oxygen be admitted, the precipitate redissolves completely, using up a volume of oxygen double that of the
phosphine absorbed in the first place.
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