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Transformation of Hydroxyapatite to Fluorapatite
Author(s) -
Wier D. R.,
Chien S. H.,
Black C. A.
Publication year - 1972
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1972.03615995003600020024x
Subject(s) - fluorapatite , fluoride , chemistry , logarithm , apatite , solubility equilibrium , solubility , solid solution , calcium , mineralogy , nuclear chemistry , inorganic chemistry , mathematics , organic chemistry , mathematical analysis
When solid hydroxyapatite and solid calcium fluoride were equilibrated at 25C with dilute solutions of HCl, analysis of the solutions yielded an average value of 118.8 for the negative logarithm of the ion‐activity product for fluorapatite (10 pCa + 2 pF + 6 pPO 4 ). This value compares favorably with values of 118.4, 119.2, and 120.9 reported by other investigators for the negative logarithm of the activity solubility‐product constant for fluorapatite. A plot of the negative logarithm of the activity‐product of (H) 3 (PO 4 ) against the negative logarithm of the activity‐product of (Ca)(OH) 2 in solution yielded a regression line with a slope of −1.52, which is close to the theoretical value of −1.50 for fluorapatite in a solution saturated with calcium fluoride and is greater than the theoretical value of −1.67 for hydroxyapatite. The results indicate that at least the surface of the hydroxyapatite had been converted to fluorapatite during the equilibration with solid calcium fluoride.