Abstract: The partial thermodynamic functions of solvent and solutes in multicomponent systems have been expressed in terms of the interaction parameters. The corresponding analytical expressions of the activity coefficients of solvent and solutes enable to de scribe the thermodynamic properties of multicomponent systems. The advantages of this treatment are found in its thermodynamic consistency and a rather small influ ence of the higher order interaction parameters on the properties of the systetms.

Key words: thermodynamics, activity, model