An alternative gibbs-duhem method for the calculation of activities from the redox data for iron oxide in ternary oxide systems

An alternative approach is presented in this article for the calculation of the activity of FeO, Fe₂O₃, and the other component in ternary oxide slags when the redox behavior of iron oxides is known. The approach avoids the use of the “tangent intercepts” to the iso-oxygen activity curves as required in Schuhmann's method. Favorable comparisons were obtained for the systems of FeO-Fe₂O₃-CaO and FeO-Fe₂O₃-SiO₂ between the isoactivity curves derived using this method and those established in previous work using Schuhmann's method. Direct calculation of the free energy of mixing from the redox data is also possible. An example is given for the FeO-Fe₂O₂-CaO system.