Activity measurement of CaO-SiO₂-AlO_1.5-MgO slags equilibrated with molten silicon alloys

The activities of components in the CaO-SiO₂-AlO_1.5-MgO slags at 1 823 and 1 873 K were directly measured by equilibrating the slags with Si based alloys. For the CaO-SiO₂, CaO-SiO₂-AlO_1.5 and CaO-SiO₂-MgO systems, thermodynamic properties of Si based alloys and the activity data of SiO₂ obtained from the distribution of each element between slags and the alloys in the previous paper were used to derive the activities of AlO_1.5, CaO and MgO. For the CaO-SiO₂-AlO_1.5-MgO quaternary system, the activities of components other than SiO₂ on the 10 mass% MgO plane were determined at 1 873 K by employing the SiO₂ activities available in the literature. Accordingly, it was confirmed that the activities of components other than SiO₂ in multi-component silicate stag systems can be determined by this technique as long as the activity datum of at least one component in the systems is available.