A FORTRAN IV program developed by Gordon and McBride (1971) was extensively modified to compute solid-vapor chemical equilibrium in multi component systems at a given temperature and pressure. The program is based on minimization of the Gibbs free energy of the system. Fugacity coefficients of gases and molar volumes of solids are considered. Test cases were run to compare the computed results with experimentally derived results. The systems SiO₂, MgO-SiO₂, CaO-SiO ₂, MgO-H₂O, CaO-H₂O, MgO-CO₂, H₂O-CO₂-MgO and tremolite-CO₂-H₂O were studied and it was found that the calculated results of most of these systems compared favorably with previous work. Discrepancies in the results are believed due to inaccurate thermodynamic or molar volume data. In order to study some of the binary systems at different pressures it was necessary to extrapolate the available thermodynamic data to higher temperatures. The method of extrapolation used appears to be successful and can probably be used for other species. Two secondary programs were developed which would reduce thermodynamic data of a species to a set of 14 coefficients and compute Gibbs free energy of a species at any temperature from the coefficients.

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