Cupric hypophosphite

Cupric hypophosphite, Ch HgPOg) —The solution obtained by addition of slightly less than the equivalent proportion of barium hypo-phosphite to a solution of cupric sulphate yields, after removal of the barium sulphate and addition of alcohol, the hypophosphite in the form of white crystals.4 At ordinary temperatures the dry salt does not decompose for several days, but at 90° C. it explodes with evolution of phosphine. On warming in aqueous solution, it decomposes with formation of phosphorous acid, copper, and hydrogen. Its aqueous solution is also decomposed catalytically by palladium ... 

According to H. Rose, the blue soln. of cupric hydroxide in cold hypophosphorous acid may remain unaltered for a long time and if very dil., it may even be heated without decomposition. If the soln. be evaporated in vacuo at a low temp., the copper is completely reduced as soon as the liquid is highly concentrated. C. A. Wurtz found that the soln. obtained by double decomposition of barium hypophosphite and copper sulphate at about 60° precipitates copper hydride— vide supra. Once blue crystals of copper hypophosphite, Cu(H2P02)2, were obtained they decomposed abruptly at 65°. According to R. Engel, this salt... 

It is also reduced to metallic gold by phosphorous acid and sodium hypophosphite, and by cupric sulphide in accordance with the equation10... 

Characteristically, too, the addition of cupric ions inhibits completely this polymerization induced by hypophosphite and an oxidizer. Consequently, the reactions... 

Hypophosphites are more powerful reducing agents than phosphites. The acid will reduce sulphur dioxide to sulphur and will precipitate Pt, Au, Ag, Hg and Bi from aqueous solutions of these salts. Hypophosphites reduce cupric salts to cuprous and dichromates to trivalent chromium salts. 

Phosphites and hypophosphites both decolourise acidified potassium permanganate solutions, but only the latter reacts in the cold. Phosphites can be distinguished from hypophosphites by their reaction with copper sulphate solution. The former will give a light blue precipitate of cupric phosphite, while the latter will give a reddish precipitate of copper hydride on warming. 

Salts of noble metals must be absent since they are reduced by hypophos-phite to the finely divided, intensely colored metal and may hide the Sn -cacotheline reaction. Silver salts and, to a greater extent, osmium salts, reduce the catalytic action of mercury. Cupric salts are reduced by hypophosphite to cuprous salts and in this state react with cacotheline in the same way as Sn salts. 

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