Solubility Behaviour of Mg‐Containing β‐Ca3 (PO4)2

The solubilities of synthetic β‐Ca3 (PO4)2 [TCP] and Mg‐containing β‐Ca3 (PO4)2 [TCMP] were determined in the system Ca(OH)2‐Mg(OH)2‐H3PO4‐KCl‐H2O at 25° C. The thermodynamic solubility product of TCP is found to be (1,14 ± 0.10) x 10−30 mol5. l−5. The incorporation of Mg2+ results in a remarkable stabilization of the β‐TCP structure as reflected by a drastic decrease in the amount of solid dissolved for TCMP compared to that for TCP and by the fact that the solutions are undersaturated with respect to calciumhydroxyapatite. On the basis of solid state chemical and thermodynamical principles the solubility behaviour of TCMP solid solutions is discussed. Indications are found that magnesium whitlockite possibly precipitates during the equilibrations of TCMP.