Potentiometric Determination of the Gibbs Free Energy of Formation of Cadmium and Magnesium Chromites

The standard Gibbs free energy of formation of magnesium and cadmium chromites have been determined by potentiometric measurements on reversible solid‐state electrochemical cells in the temperature range 500°–730°C, and in the temperature range 800°–1200°C. The temperature dependence of the free energies of formation of the ternary compounds can be represented by the equations and The entropies of formation of these spinels are discussed in terms of cation disorder and extent of reduction of Cr 3+ ions to Cr 2+ ions. Thermodynamic data on the chromates of cadmium and magnesium are derived by combining the results obtained in this study with information available in the literature on high temperature, high pressure phase equilibria in the systems and .