Further improvements to the modified quasichemical model in the pair approximation for short-range ordering in liquid and solid solutions are presented. The energy of pair formation is expanded in terms of the pair fractions rather than the component fractions, and coordination numbers are permitted to vary with composition. A formalism is introduced whereby the quasichemical equations are shown to be equivalent to the equations of an associate model if the pairs are formally treated as fractional associates. The model is applied to the liquid phase in a new optimization of the KCl-MgCl 2 system.

2941electrochemica ! transport that occurs during EVD is similar to the phenomena of oxygen semipermeability wherein electrons migrate from the low oxygen partial pressure side to the high oxygen partial pressure side and oxygen ions migrate in the reverse direction maintaining electroneutrality. AcknowledgmentsThe authors would like to acknowledge the dedicated efforts of G. R. Folser and J.A. Fraino in conducting the EVD experiments and Mrs. J. A. Radford for her patience in typing the manuscript. The help of T. A. Manion in preparing the metallographic mounts and R. W. Palmquist in analyzing the samples with electron microprobe is greatly appreciated. ABSTRACTThe thermodynamic properties and phase diagrams of the nine common-ion binary systems of alkali carbonates' and sulfates have been critically evaluated by the technique of computer-assisted simultaneous optimization. Coefficients of series expansions for the excess thermodynamic properties of all phases have been found which can be used to reproduce the thermodynamic properties and to calculate the phase diagrams within experimental error limits. Henrian activity coefficients of dilute solid solutions and Gibbs energies of formation of compounds have also been determined. The resultant calculated thermodynamic properties and phase diagrams are self-consistent, and represent the best estimates which can be made based on currently available data. A consistent set of values for the thermodynamic properties of the pure salts has also been adopted, and some thermodynamic properties of the pure alkali carbonates and sulfates have been revised.Molten salt systems involving carbonates and sulfates are of importance in hot corrosion, in electrochemical cells such as the molten carbonate fuel cell, and in many chemical and metallurgical applications. The present article reports critical, coupled evaluations of phase diagram and thermodynamic data for the nine common-ion binary sysl Permanent address: Sangster Research Laboratories, Montreal, Quebec, Canada H3G 2A4.tems involving the carbonates and sulfates of lithium, sodium, and potassium.A complete literature survey has been carried out for the nine systems treated in this article, for both phase diagram and thermodynamic data. Coefficients of Gibbs energy expressions which represent the thermodynamic and phase diagram data within experimental error have been found by computer optimization. This calculation uncovers discrepancies among the data and generates analytical ex-) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-26 to IP

The modified quasichemical model for short-range ordering is described for liquid metal-sulfur solutions. Available thermodynamic data for molten Fe-S, Ni-S, Cu-S, and Co-S solutions are collected, critically evaluated, and optimized by means of the model. Very good descriptions of the thermodynamic properties are obtained with few parameters. Using only these binary parameters, the model predicts the thermodynamic properties of Fe-Ni-S, Fe-Cu-S, Ni-Cu-S, and Fe-Ni-Cu-S mattes over a wide range of composition and temperature within experimental error limits.

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