ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Determination of the enthalpy of crystallization of eutectic melt in the system 2CaO.Al₂O₃.SiO₂ - CaO.Al₂O₃. 2SiO₂

L. Kosa, O. Žigo, K. Adamkovičová, and I. Proks

Institute of Inorganic Chemistry, Centre for Chemical Research, Slovak Academy of Sciences, CS-84236 Bratislava

Abstract: Using a precursor method the melt of eutectic composition in the system 2CaO • Al₂O₃ • SiO₂ - CaO • Al₂O₃ • 2SiO₂ (30.34 mass % CaO; 36.91 mass % Al₂O₃ ; 32.75 mass % Si0₂ ) and one of the products of its crystallization, viz. CaO • Al₂O₃ • _.2SiO₂, were prepared. The temperature dependence of the spe­ cific relative enthalpy of the eutectic melt was determined using combination of the experimental data obtained in "drop" calorimeter and in the cal­orimeter for determination of heats of dissolution. The temperature depen­ dences of the specific relative enthalpy of the products of crystallization of the eutectic melt (these products being 2CaO •  Al₂O₃ • Si0₂ (gehlenite) and CaO •  Al₂O₃ • 2Si0₂ (anorthite)) were determined on the basis of literature data and the measured value of the specific heat of dissolution of CaO • Al₂O₃ • 2Si0₂ . On the basis of the values of the specific relative enthalpy of the eutectic melt and of the phases 2CaO • Al₂O₃  • Si0₂ and CaO • Al₂O₃ • 2Si0₂ related to the equilibrium temperature of crystallization of the eutectic melt 1658 К and from the material balance of the crystallization process the value of the specific enthalpy of crystallization of the eutectic melt was determined ∆h_cryst(eut. melt; 1658K) = (- 441 ± 23) kJ kg^-1 The error was determined on the level of significance equal to 95 %.

Full paper in Portable Document Format: 413a289.pdf

Chemical Papers 41 (3) 289–298 (1987)