Abstract: The molecular interaction vacancy model (MIVM) is used to estimate simultaneously activities of all components in a range of entire composition of six binary oxide solid solutions and the MnO-FeO-CaO ternary solid solution by their binary infinite dilute activity coefficients. The average errors are the 0.03%--5.0% for the binaries and the 4.11%--25.2% for the ternary which is less than that (4.84%--41.2%) of the sub-regular solution model (SRSM). This shows that MIVM is more effective and reliable than SRSM for the ternary and does not depend on a polynomial approximation with some ternary adjustable parameters.

Key words: Estimation, Activity, Oxide, Solid solution, Thermodynamic model