Calcium Phosphates

Tertiary or normal calcium phosphate, Ca3(PO4), is found in nature as APATITE and PHOSPHORITE (q.v.). It is one of the chief constituents of animal bones. Not soluble in water, but can be converted into a soluble form by treatment with sulphuric acid. Its principal use is for the manufacture of artificial fertilizers. Secondary calcium phosphate, CaHPO4,+2H2O, is sometimes found in guano, and made by treating a solution of a calcium salt with secondary sodium phosphate. Primary calcium phosphate, CaH4(PO), is soluble in water and used extensively as a fertilizer. Made by treating the normal phosphate with sulphuric acid. The mixture of this phosphate and calcium sulphate is sold as "superphosphate of lime," as an agricultural.