Thermochemical studies on amorphous calcium phosphate (original) (raw)
Abstract
Previous studies have indicated that synthetically-precipitated amorphous calcium phosphate, even though not a periodically regular structure, possesses a chemically definable local unit of structure. The present paper is a report of thermochemical studies performed to more clearly define this local chemical unit. Upon ignition in the absence of water, freezedried amorphous calcium phosphate preparations converted into crystalline α-and/or β-tricalcium phosphates. At temperatures just below the crystallization point, the amorphous calcium phosphate became almost completely dehydrated. Additionally, pyrophosphate production at these subcrystallization temperatures was very low. From these data, it appears that water in amorphous calcium phosphate does not exist in combination with the P2O5 component as acid phosphate but retains its molecular identity, suggesting, together with previously reported chemical data, that amorphous calcium phosphate when formed under specific chemical conditions is a hydrated tricalcium phosphate.
Résumé
Des études antérieures ont montré que le phosphate de calcium amorphe précipité, de facon synthétique, bien que ne présentant pas une structure périodique régulière, présente cependant une structure chimiquement définie. Le présent travail est consacré à des études thermo-chimiques destinées à définir plus clairement une telle structure. Au cours d'ignifugation en l'absence d'eau, les préparations de phosphate de calcium amorphe, après congélationdessication, se transforment en phosphates tricalciques cristallins α et β. A des températures situées immédiatement au-dessous du point de cristallisation, le phosphate de calcium amorphe se déshydrate presqu'en totalité. En plus, la production de pyrophosphate à ces températures de subcristallisation est très basse. D'après ces résultats, il apparait que l'eau du phosphate de calcium amorphe n'existe pas en combinaison avec le composant P2O5, en tant que phosphate acide, mais conserve son identité moléculaire. Ce fait semble indiquer, en accord avec des résultats chimiques antérieures, que le phosphate de calcium amorphe est un phosphate tricalcique hydraté, lorsqu'il est obtenu dans des conditions chimiques spécifiques.
Zusammenfassung
Frühere Untersuchungen haben gezeigt, daß künstlich gefälltes, amorphes Calciumphosphat eine chemisch definierbare Struktureinheit besitzt, obschon diese nicht periodisch einheitlich ist. Die vorliegende Arbeit beschreibt thermochemische Untersuchungen, die zur besseren Definierung dieser chemischen Struktur durchgeführt wurden. Durch Erhitzen in Abwesenheit von Wasser verwandelten sich gefriergetrocknete amorphe Calciumphosphatproben in kristallines α-und/oder β-Tricalciumphosphat. Bei Temperaturen gerade unter dem Kristallisationspunkt wurde das amorphe Calciumphosphat beinahe vollständig dehydriert. Dazu war die Pyrophosphatbildung bei diesen Temperaturen sehr gering. Aus diesen Resultaten zu schließen, scheint es, daß das Wasser im amorphen Calciumphosphat nicht in Verbindung mit der P2O5-Komponente als saures Phosphat besteht, sondern seine molekulare Identität beibehält. Dies läßt vermuten, gestützt auch auf früher mitgeteilte chemische Ergebnisse, daß unter spezifisch chemischen Bedingungen gebildetes amorphes Calciumphosphat ein hydriertes Tricalciumphosphat ist.
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Authors and Affiliations
- Crystal Chemistry Section, Laboratory of Biological Structure, National Institute of Dental Research, National Institutes of Health, 20014, Bethesda, Maryland, U.S.A.
E. D. Eanes
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Eanes, E.D. Thermochemical studies on amorphous calcium phosphate.Calc. Tis Res. 5, 133–145 (1970). https://doi.org/10.1007/BF02017543
- Received: 12 August 1969
- Accepted: 31 October 1969
- Issue date: December 1970
- DOI: https://doi.org/10.1007/BF02017543