Amorphous calcium phosphate
Amorphous calcium phosphate (ACP or ATCP) is a glassy precipitate of variable composition that is formed in double decomposition reactions involving a soluble phosphate and calcium salts (e.g. (NH4)2HPO4 + Ca(NO3)2) performed under carefully controlled pH conditions. The precipitate will either be "amorphous tricalcium phosphate", ATCP, or calcium deficient hydroxypatite, CDHA, Ca9(HPO4)(PO4)5(OH), (note CDHA is sometimes termed apatitic calcium triphosphate). The composition of amorphous calcium phosphate is CaxHy(PO4)z· nH2O where n is between 3 and 4.5. Precipitation from the moderately supersaturated and basic solution containing magnesium, led the precipitation of amorphous magnesium calcium phosphate (AMCP) in which magnesium incorporated into the ACP structure.