Enthalpie De Formation Et De Melange De Phosphoapatites Calco-Cadmiees Chlorees |
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Authors: | A. Ben Cherifa M. Jemal |
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Affiliation: | (1) Faculté des Sciences de Tunis, Département de Chimie, Laboratoire de Thermodynamique Appliquée, 1060 Tunis, Tunisie |
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Abstract: | Calcium–cadmium chlorapatites solid solutions with the general formula Ca10–xCdx(PO4)6Cl2,1≤x≤10, were prepared by solid state reaction and characterized by X-ray diffraction, infrared spectroscopy and chemical analysis. Using an isoperibol calorimeter, their enthalpies of solution in 9 mass% nitric acid were measured. In order to determine the enthalpies of formation and enthalpies of mixing, thermochemical cycles were proposed and complementary experiences were performed. The results obtained show a decrease of the enthalpy of formation with the amount of cadmium introduced in the lattice. The variation of mixing enthalpy vs. x=Cd/(Cd+Ca) shows a maximum at about x=0,4. This could be explained by the existence of two cationic sites in the phosphoapatite structure. This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | calcium– cadmium chlorapatite enthalpy of formation enthalpy of mixing |
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