Activity of CaO in the Slag of CaO-SiO₂-Al₂O₃ System

Abstract

Our previous reports described the results of determination of the activity of SiO₂ and Al₂O₃ in the slag of CaO-SiO₂-Al₂O₃ system using the e.m.f method of double cell. As it is difficult to construct the cell with reversible calcium electrode at high temperature, the authors tried to determine the activity of CaO with solid lime at 1630° as the standard using Gibbs-Duhem equation. At first, the activity of CaO on the system CaO-Al₂O₃ was determined. Then the same calculation was extended to CaO-SiO₂-Al₂O₃ and CaO-SiO₂ systems. From these value, the iso-activity lines were drawn on the ternary coordinates of CaO-SiO₂-Al₂O₃. The course of iso-a_CaO line was similiar to the so-called sulphur capacity lines. From the activity-composition diagram on the system CaO-SiO₂, a_CaO saturated with 2CaO.SiO₂ was given as 0.25.