Solubility and surface properties of finely divided hydroxyapatite
- 1 January 1973
- journal article
- Published by National Institute of Standards and Technology (NIST) in Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
- Vol. 77A (1) , 149-155
- https://doi.org/10.6028/jres.077a.008
Abstract
Synthetic hydroxyapatite (OHAp), Ca5(PO4)3OH, was prepared by slow addition of phosphoric acid to a boiling Ca(OH)2 suspension. The solid, precipitated at a pH of about 12, was stabilized by prolonged boiling. The Ca/P ratio of the product was 1.69 ± 0.04 and it had a specific surface area of 26 m2/g. Samples of OHAp were equilibrated with phosphoric acid solutions. Within the pH range studied, 5 to 7, the solubility product, (Ca)5(PO4)3(OH), was found to be 6.3 ± 2.1 × 10-59 at 25 °C. Substantial deviations of the overall dissolution reaction from OHAp stoichiometry were observed and are attributed to nonstoichiometric reactions occurring at the surface. A linear dependence of excessive phosphorus on the surface with decrease in pH was found. Estimates on the extent of deviation from stoichiometry caused by the surface reaction are given.Keywords
This publication has 1 reference indexed in Scilit:
- Infra-red spectra of hydroxyapatite, octacalcium phosphate and pyrolysed octacalcium phosphateArchives of Oral Biology, 1966