Surface structure of amorphous calcium phosphate by ESR of VO2+ adsorbed on it.

The electron spin resonance (ESR) spectra of vanadyl ions (VO2+) adsorbed on amorphous calcium phosphate (ACP), formed under varying conditions, were measured at room temperature. They varied with the variation of the conditions and were different from those of other calcium phosphates. The present result suggests that ACP is a distinct and a separate compound from other calcium phosphates and that ACP is a noncrystalline form of Ca3 (PO4)2 X 3 H2O or a solid solution of the composition of Ca3(PO4)1.87(HPO4)0.2, which was proposed previously.