EFFECT OF ETHANOL ON THE FORMATION OF CALCIUM PHOSPHATES

In both aqueous and ethanol-water solutions, the first precipitate fro m a highly supersaturated calcium phosphate solution was amorphous cal cium phosphate (ACP) at pH 7.4 and higher. The Ca/P ratio of ACP incre ased with the increasing pH from 1.28 at pH 7.4 to 1.50 at pH 10.2. In aqueous solutions, ACP rapidly transformed to poorly crystallized hyd roxyapatite (PCHA) at pH 7.4. In the ethanol-water solutions, this tra nsformation was slowed down at pH 7.4, but it was accelerated with the addition of 8.9 ppm fluoride or at lower pH of 7.1. The ethanol favor s the formation of ACP by the increase in the degree of supersaturatio n and precipitation rate, and more rapid drying of the precipitated so lids. The fluoride and lower pH promote the formation of apatite by sh ortening the life-time of the ACP.