Dicalcium phosphate
Dicalcium phosphate is the calcium phosphate with the formula CaHPO4. The "di" prefix in the common name arises because the formation of the HPO4 anion involves the removal of two protons from phosphoric acid, H3PO4. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. There are three crystalline forms: a dihydrate, CaHPO4•2H2O ('DPCD'), the mineral brushite; a hemihydrate, CaHPO4•0.5H2O; and anhydrous CaHPO4, ('DCPA'), the mineral monetite. Below pH 4.8 the dihydrate and anhydrous forms of dicalcium phosphate are the most stable (insoluble) of the calcium phosphates. Dicalcium phosphate is used as a food additive, it is found in some toothpastes as a polishing agent and is a biomaterial. In the dihydrate (brushite) form it is found in some kidney stones and in dental calculi.