Clustering of calcium phosphate in the system CaCl2-H3PO4-KCl-H2O

The stability of calcium phosphate clusters approximately 0.8 nm in diamete r, which were found in a simulated body fluid in a previous work, was inves tigated in the system CaCl2-H3PO4-KCl-H2O using an intensity-enhanced dynam ic light-scattering technique at 25 degrees C. It was shown that tris(hydro xymethyl)aminomethane, which was used as a buffer in the previous study, ha d no effect on the formation of the clusters. The amount of clusters decrea sed with decreasing supersaturation of the solution with respect to hydroxy apatite. Under constant supersaturation with respect to hydroxyapatite, the amount of the clusters reached a maximum in solutions with Ca/P molar rati os ranging from 1 to 8.