{"title":"Orthophosphates. Part II. The transformations brushite → fluoroapatite and monetite → fluoroapatite in aqueous potassium fluoride solution","authors":"E. J. Duff","doi":"10.1039/J19710000033","DOIUrl":null,"url":null,"abstract":"The transformations brushite → fluoroapatite and monetite → fluoroapatite have been investigated at 25 °C in aqueous acidic KF solutions, ca. 10–1M in F–. The transformations involve a first-order uptake of F– by the secondary orthophosphates, followed by a solid-state rearrangement to fluoroapatite with the second-order release of H2PO4–. The ΔGf° for fluoroapatite has been calculated from the brushite → apatite transformation as –1524·1 kcal mol–1, and confirmed by calculation of the ΔGf° value for monetite as –401·1 kcal mol–1. From these results, the ΔGf° values of hydroxyapatite, Ca5OH(PO4)2, Ca3(PO4)2, and Ca(H2PO4)2, and Ca(H2PO4)2,H2O were calculated as –1494·2, –925·1, –677·8, and –729·5 kcal mol–1. The possibility of K substitution for Ca in fluoroapatite is discussed.","PeriodicalId":17321,"journal":{"name":"Journal of The Chemical Society A: Inorganic, Physical, Theoretical","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"34","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of The Chemical Society A: Inorganic, Physical, Theoretical","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1039/J19710000033","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 34
Abstract
The transformations brushite → fluoroapatite and monetite → fluoroapatite have been investigated at 25 °C in aqueous acidic KF solutions, ca. 10–1M in F–. The transformations involve a first-order uptake of F– by the secondary orthophosphates, followed by a solid-state rearrangement to fluoroapatite with the second-order release of H2PO4–. The ΔGf° for fluoroapatite has been calculated from the brushite → apatite transformation as –1524·1 kcal mol–1, and confirmed by calculation of the ΔGf° value for monetite as –401·1 kcal mol–1. From these results, the ΔGf° values of hydroxyapatite, Ca5OH(PO4)2, Ca3(PO4)2, and Ca(H2PO4)2, and Ca(H2PO4)2,H2O were calculated as –1494·2, –925·1, –677·8, and –729·5 kcal mol–1. The possibility of K substitution for Ca in fluoroapatite is discussed.