Free energy of mixing of divalent basic oxides with silica

Abstract

An expression derived for the free energy of mixing of a divalent basic oxide (MO) with SiO₂ based on a model of silicate structure, takes into account the distribution of O^2–(from MO) into the silica network, the mixing of silicate ions with O^2– and the enthalpy of mixing. The resulting expression is [graphic omitted].

For the proper choice of β, calculated values of the activity of MO for the system PbO—SiO₂, MnO—SiO₂, FeO—SiO₂ and CaO—SiO₂ are in good agreement with experiment. The model predicts that the activity of the basic oxide decreases with increase in temperature.