Description
Calcium hypophosphite has the molecular formula of Ca(H2PO2)2 and the molecular weight of 170.0631 g/mol. This salt can be prepared by the aqueous reaction of the carbonate or oxide with H3PO2:
CaO + 2H3PO2 ? Ca(H2PO2)2
The salt is soluble in water (20 g/100 ml at 20°C) so that the solution must be evaporated to obtain crystals. Ca(H2PO2)2 has the CAS number of 7789-79-9 and the density of 1.59 g/cm3. It is composed of white square monoclinic crystalswhich are water soluble. It is insoluble in alcohol or ether.When heated to about 305°C, it disproportionates, forming calcium phosphate and phosphine:
Ca(H2PO2)2 + heat ? CaHPO3 + PH3
Chemical Properties
white monoclinic, prismatic crystal(s) or granular powder(s); used as a corrosion inhibitor and in medicine [MER06] [HAW93]
Physical properties
Calcium hypophosphite is relatively soluble in water, and when added to a solution of sodium hypophosphite, forms a double salt. Crystals were obtained by slow evaporation of the solution to form dodecahedra with well-developed {110} faces. The crystal structure of CaNa(H2PO2)3 belongs to the cubic system with space group, P213, Z = 4 and a = 9.721?. The structure consists of two kinds of octahedral groups, one with a calcium atom and the other with a sodium atom. Each atom of the hypophosphite ions is coordinated to each one of the calcium and sodium atoms to form the octahedral. This structure is, in general, typical of the salts of hypophosphorous acid.
Calcium hypophosphite is readily available commercially since its main usage, both industrially and in Research, has proven to be as a source of hypophosphite anions to form other hypophosphites.
Uses
As corrosion inhibitor; in nickel plating. Pharmaceutic aid (retards oxidation of ferrous salts).
China
