Hydrothermal synthesis studies in portions of the system CaO—P2O5–H2O—CO2–F have produced apatites with composition variations. The lattice constants of the apatites have been determined using computer analyses of x-ray powder diffraction data. By this method compositional fluctuations of a phase within a mixture containing several phases can be monitored. Lattice characteristics of hydroxyapatite (molar CaO/P2O5=3.3) synthesized at pressures of 2000 bars and temperatures from 300° to 800°C from bulk compositions over the range 2.0 to 5.0 CaO/P2O5 are discussed.
