Lewis-Randall to McMillan-Mayer Conversion for the Thermodynamic Excess Functions of Solutions. Part I. Partial Free Energy Coefficients

Derivations are given for the thermodynamic relations that are needed to compare experimental thermodynamic excess functions of various kinds with the corresponding functions obtained from models for the solutions by calculations made in the framework of the McMillan-Mayer theory. This contribution extends earlier results. The new results are used to elucidate the behavior of the McMillan-Mayer thermodynamic excess functions of solutions which are very nearly ideal on the mole-fraction scale, for example, isotope mixtures. The study of these ideal systems leads to the conclusion that liquid-structure effects associated with the packing of molecules contribute a negative term to the potential of the force between solute particles in the solvent.