Thermodynamics of redox reactions between oxides of glass melt and oxygen: II. Equilibrium of iron and manganese oxides with oxygen

The thermodynamic approach developed in the preceding paper with respect to chemical transformations is applied to the equation of reaction between iron or manganese oxides and oxygen in a glass melt. This equation of reaction is treated in terms of the mass action law. The transition of liquid iron (FeO and Fe2O3) and manganese (MnO and Mn2O3) oxides into a glass melt is accounted for by the oxide activity coefficients. The equations that relate the ratios q(M) = x(M2O3) /x(MO)(2) and (RC)(M) = x(M2O3)/x(MO) [where x(M2O3) and x(MO) are the mole fractions of the Fe2O3 (Mn2O3) and FeO (MnO) oxides in a melt, respectively] to the temperature, partial pressure of oxygen, and total oxide content in a melt x(M) = x(M2O3) + x(MO) are derived. These equations are used in analyzing the experimental data available in the literature on the equilibrium concentrations of iron and manganese oxides (x(M2O3) and x(MO)) in melts of oxide glasses. In particular, it is demonstrated that the obtained equation describing the dependence of (RC)(Fe) on X-Fe = X-Fe2O3 + X-FeO predicts an increase in (RC)(Fe) with a rise in X-Fe, which is in agreement with the experimental data for model and commercial glasses.