We describe a thermodynamically consistent 2nd-order truncated composition-expansion for the species residual partial molar properties ⎯ including volume, enthalpy, entropy, and Gibbs free energy ⎯ of dilute ternary systems aimed at the molecular account of solvation phenomena in any type of systems and regardless of the type of intermolecular forces involved (Chialvo, Chialvo et al. 2008). Because the expansion is performed around the infinite dilution reference, we show how the expansion coefficients can be microscopically and explicitly interpreted in terms of direct and total correlation function integrals over the microstructure of the reference system, as well as their pressure and temperature derivatives, according to our previously derived solvation formalism for infinite dilute solutions (Chialvo and Cummings 1994).

To illustrate the relevant features of expansions we (a) highlight with examples from the literature the thermodynamic inconsistencies encountered in the currently available 1st-order truncated expansions, that render them invalid, (b) illustrate how our formal expressions converge, at the zero density limit, to those for multicomponent mixtures of imperfect gases obeying the virial equation of state Z=1+BP/kT, (c) derive the corresponding consistent counterparts for binary mixtures as a ‘special' case of the original ternary systems, and (d) use integral equation calculations for the direct prediction of the species partial molar properties from the knowledge of the effective intermolecular interactions.

Chialvo, A. A., S. Chialvo, Y. V. Kalyuzhnyi, and J. M. Simonson (2008). "Solvation Phenomena in Dilute Multicomponent Solutions. I. Formal Results and Molecular Outlook." Journal of Chemical Physics (In press).

Chialvo, A. A. and P. T. Cummings (1994). "Solute-induced Effects on the Structure and the Thermodynamics of Infinitely Dilute Mixtures." Aiche Journal 40: 1558-1573.