Abstract
xH2O and Ca9-x (HPO4)1+2x (PO4)5-2x OH in which1≥ x ≥ 0 in both cases. No evidence could be found spectroscopically for the previously proposed, octacalcium phosphate-hydroxy apatite lamellae amongst the calcium deficient apatites studied. The infra-red and thermal data obtained during this study were both consistent with a system of isomorphous substitution of Ca2+, OH and H+ ions in an apatite lattice.