Abstract
Octacalcium phosphate[Ca_8H_2(PO_4)_6・5H_2O, hereafter referred to as OCP]was synthesized at 30〜80℃ by the reaction of an aqueous suspension of dicalcium phosphate dihydrate(DCPD)and calcium carbonate.Thin blade crystals of OCP were formed on the crystal plate of DCPD, and were converted to hydroxyapatite(HA)as time elapsed at 50〜80℃.The converted HA was calcium-deficient hydroxyapatite with a Ca/P ratio of about 1.5.The X-ray diffraction intensities during decrease of DCPD and increase of both OCP and HA changed proportionally to the square root of reaction time and these change rates depended upon the reaction temperature.These findings suggest that the rate-determining step of this successive reaction is the diffusion of calcium ions through the Nernst boundary layer around each crystal particle.
