The precipitation kinetics of calcium phosphates, namely, hydroxyapatite (HAP), dicalcium phosphate dihydrate (DCPD), dicalcium phosphate anhydrous (DCPA), and monocalcium phosphate monohydrate (MCPM), were studied at 30°C by mixing calcium hydroxide, water, and phosphoric acid. The studied mixture was selected according to the stability domain of different calcium phosphates by referring to the phase diagram of the ternary system of H3PO4-Ca(OH)2-H2O at 30°C. The precipitation reaction has been monitored by following the changes in the conductivity, pH, and calcium concentration. The solid phases formed at different stages of this precipitation were characterized by X-ray diffraction.

The solid-liquid phase equilibria of the system H3PO4-Ca(OH)2-H2O were studied under air pressure using a synthetic method based on conductivity measurements. Two isotherms at 15 and 45 °C were completely defined. The stable solid phases which appear in this range of temperature are hydroxyapatite (Ca10(PO4)6(OH)2), calcium hydrogen phosphate dihydrate (CaHPO4.2H2O), calcium hydrogen phosphate anhydrous (CaHPO4) and calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2.H2O). These solid phases were characterized using X ray diffraction.

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