Enthalpy of mixing of liquids in the system CaMgSi₂O₆–CaAl₂Si₂O₈

Author： Sugawara Toru Nakagawa Shinsuke Yoshida Satoshi Matsuoka Jun

ISSN： 0031-9090

Source： Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B, Vol.50, Iss.6, 2009-12, pp. : 384-388

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Abstract

Enthalpy differences between liquids at 1773 K and glasses at 273 K in the diopside (CaMgSi₂O₆)–anorthite (CaAl₂Si₂O₈) system have been measured by drop calorimetry. Enthalpies of dissolution of the drop quenched glasses were measured by HF solution calorimetry at 298 K. Enthalpies of mixing of liquids are determined from the combination of both results. The enthalpy of mixing shows asymmetric composition dependence, which can be expressed asH^L_Mix=χ^L_Diχ^L_An(−80X^L_Mix+30χ^L_An) kJ/molwhere χ^L_Di and χ^L_An represent mole fractions of CaMgSi₂O₆ and CaAl₂Si₂O₈, respectively. The asymmetric enthalpy of mixing should be associated with the competition between endothermic enthalpy by network strain at Al-rich composition and exothermic enthalpy by network breaking at Mg-rich composition.