イオン交換樹脂を含む懸濁水への難溶性無機化合物の溶解(第11報)

—リン酸八カルシウム (Ca₈H₂(PO₄)₆•5H₂O)—

抄録

The dissolution process of octacalcium phosphate (Ca₈H₂(PO₄)₆•5H₂O, OCP) using a strongly acidic ion exchange resin with a hydrogen form (H-R) suspended in water was examined in detail to confirm the formation of CaHPO₄•2H₂O (DCPD) as an intermediate. The reactivity of OCP, α- or β- tricalcium phosphate (α- or β-TCP), or tetracalcium phosphate (Ca₄(PO₄)₂O, TetCP), with Ca(H₂PO₄)₂ solution to form DCPD was compared using calorimetry and chemical analysis. The reactivity increased in the order of TetCP=α-TCP»OCP≥β-TCP. The structure of OCP consists of “apatite layer” and “hydrated layer.” The “apatite layer” of OCP was examined by comparing the reactivity of DCPD+hydroxyapatite (HAp) and DCPD+β-TCP with H-R where HAp and β-TCP imitated the “apatite layer.” The results suggested that the “apatite layer” in OCP would be similar to β-TCP rather than HAp in terms of the reactivity.