Calcium hypophosphate has the molecular formula
of Ca2P2O4. It can be formed by an aqueous solution of
hypophosphorus acid and a soluble calcium salt:
2CaCl2 (aq) +H4P2O4 (aq) ? Ca2P2O4 (solid)
+ 2HCl (aq)
The calcium salt solution is added until no precipitate
results. Alternatively, sodium hypophosphate can
be used to produce a basic solution instead of acidic. The
basic product is a hexahydrate, Ca2P2O4·6H2O.
The acidic product is a dihydrate, CaH2P2O4·2H2O.
The former salt is insoluble in water but slightly soluble
in acetic acid. It redissolves in excess hypophosphoric
acid. Its CAS number is 75499-50-2. The acidic salt is
more soluble in water at 16.8 g/100 ml at 20°C. If this
salt is heated, it loses the two waters of hydration at
about 125–130°C. The crystal structure of the anhydrate
or the hydrate has not been determined.
Calcium hypophosphate has been used as a rootdesensitizing
agent in Dentistry. It has been prescribed
as a source of calcium and phosphorus in the human
body by Homopathic practioners until it was discovered
that this compound crystallizes in tissues and may add
to kidney stones and gall stones.
