Lead orthophosphates-III. Stabilities of fluoropyromorphite and bromopyromorphite at 25°C

  • Nriagu J
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The reactions of secondary lead orthophosphate with approximately 10-1M sodium fluoride and sodium bromide solutions have been investigated at 25°C. Interpretation of the solubility data resulted in solubility product constants for fluoropyromorphite and bromopyromorphite of 10-71.6and 10-78.1, respectively. According to these constants, the stability sequence for lead pyromorphites is Pb5(PO4)3Cl > Pb5(PO4)3Br > Pb5(PO4)3OH > Pb5(PO4)3F. The derived free energy data have been used to evaluate the respective stabilities of fluoro-pyromorphite and bromopyromorphite within the systems PbF2-PbO-P2O5-H2O and PbBr2-PbO-P2O5-H2O and to predict the equilibrium behavior of the Pb5(PO4)3F-Pb5(PO4)3OH solid solution under aqueous conditions. © 1973.

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  • Jerome O. Nriagu

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