A THERMODYNAMIC STUDY OF THE SYSTEM MGCL2-NACL-CACL2

The reversible EMF for the formation of MgCl2 in fused salts containing NaCl and CaCl2 was studied with a view to furthering the understanding of electrolytes of use in industrial magnesium electrolysis. Measurements were carried out in a cell with pure chlorine gas and Mg-Bi alloy as active electrode materials. The data were used to infer the Gibbs energy of mixing, the enthalpy of mixing and the entropy of mixing. These properties were used with other data to construct the liquidus surface of the ternary phase diagram. A multiple discrete complex anion (MDCA) model was proposed to interpret all thermodynamic findings. Successful correlations were obtained when both MgCl42− and CaCl42− complex anions were assumed to be in equilibrium with the elementary ions Cl−, Na+, Mg2+ and Ca2+