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

Computer Optimization of the Phase Diagrams of Alumino-Silicate Systems. 3. Regression Treatment of Peritectic Systems with Unknown Structural Parameters

M. Liška and J. Strečko

Institute of Inorganic Chemistry, Slovak Academy of Sciences, SK-842

E-mail: Iiska@uach1.savba.sk

Abstract: The phase diagram of the system CaO (C)-12CaO . 7Al₂O₃,(C₁₂A₇) with incongruently melting compound 3Ca0 . Al₂O₃ (C₃A) is described by a thermodynamic model. Unknown structural and enthalpic parameters of the model were obtained by the nonlinear regression analysis. The least-squares method gave following estimates: α₄(Al) = 0.566 +/- 0.06, ∆_fusH(C) = (140.7 +/- 2.6) kJ mol^-1, ∆_fus H(C₁₂A₇) = (57 +/- 8) kJ mol^-1,  ∆_fusH(C₃A) = (223 +/- 21) kJ mol^-1, T_fus,hyp (C₃A) = (1808 +/- 7) K. The inconsistency between the calorimetric and from the activity-composition relations deduced heats of fusion and/or heat of incongruent decomposition is critically discussed.

Full paper in Portable Document Format: 486a371.pdf

Chemical Papers 48 (6) 371–375 (1994)