Calcium Dihydrohypophosphite, Ca(H₂PO₂)₂

Calcium Dihydrohypophosphite, Ca(H₂PO₂)₂, is obtained by the action of phosphorus on boiling milk of lime, or of water on the phosphide. It forms anhydrous hexagonal monoclinic crystals, easily soluble in water, 1 part of salt to 6 of water, but insoluble in alcohol and unchanged by heat below 300° C. Above that temperature it is decomposed with loss of water and phosphoretted hydrogen, and formation of calcium pyro- and meta-phosphate, in the molecular proportions of 3 to 1.

It is employed in therapeutics.

Two double salts are known, a calcium cobalt hypophosphite, Ca₂Co(H₂PO₂)₆.2H₂O, forming efflorescent red octahedral crystals, and a calcium cadmium salt, which may, however, be a mixture.