Title: Calcium Phosphate, Monobasic
CAS Registry Number: 7758-23-8
Additional Names: Acid calcium phosphate; calcium biphosphate; monocalcium orthophosphate; monocalcium phosphate; primary calcium phosphate; "calcium superphosphate"
Molecular Formula: CaH4O8P2
Molecular Weight: 234.05
Percent Composition: Ca 17.12%, H 1.72%, O 54.69%, P 26.47%
Line Formula: Ca(H2PO4)2
Literature References: Commercial prepn for fertilizers by treating pulverized phosphate rock with H2SO4 or H3PO4: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 191-200. Laboratory prepn from CaCO3 and H3PO4: Jensen, Kathley, Inorg. Synth. 4, 18 (1953).
Properties: Monohydrate, large, shining, triclinic plates, cryst powder or granules. Non-hygroscopic when pure, but traces of impurities such as H3PO4 cause material to be deliquesc. Strong acid taste. Loses H2O at 100°, dec at 200°. d418 2.220. Moderately sol in water; sol in dil HCl or HNO3 or acetic acid.
Density: d418 2.220
NOTE: The products obtained from commercial processes are not pure monobasic calcium phosphate. The superphosphate obtained from the H2SO4 treatment is about 30% CaH4(PO4)2.H2O, 10% CaHPO4, 45% CaSO4, 10% iron oxide, silica, alumina, etc. and 5% water; it contains 18-21% available P2O5. The triple superphosphate obtained from the H3PO4 treatment contains from 43 to 50% available P2O5.
Use: Chiefly in fertilizers; as acidulant in baking powders and in wheat flours; mineral supplement for foods and feeds; in enameling.