Activity of FeO in the FeO-MgO-SiO₂ System Determined by High Temperature Mass Spectrometry

Abstract

Using the Knudsen-cell mass-spectrometric technique, coupled with an analysis based on the Gibbs-Duhem integration of mass spectral ion-intensity ratios, activities have been obtained for the molten FeO-MgO-SiO₂ system. The thermodynamic activity of FeO has been dtermined as a function of FeO content (0.1-0.9 mole fraction FeO) across the ternary section defined by an MgO to SiO₂ mole fraction ratio of unity. A significant positive deviation from ideal solution behavior is found for the FeO activity.