The physico-chemical properties play a pivotal role in interpreting the intermolecular interactions among mixed components and efforts in recent years have been directed at an understanding of such properties at microscopic and macroscopic levels. In order to gain insight into the mechanism of such interactions thermodynamic, transport and acoustic studies on binary and ternary solvent systems are highly useful.Also physico-chemical properties involving excess thermodynamic functions have relevance in carrying out engineering applications in the process industries and in the design of industrial separation processes. Information of these excess thermodynamic functions can also be used for the development of empirical correlations and improvement of new theoretical models. Estimates of ion-solvent interactions can be had thermodynamically and also from the measurement of partial molar volumes, viscosity - coefficient and limiting ionic conductivity studies. The monograph embraces a wide range of topics to study the chemical nature of the structure of solutes and solvents and their mutual and specific interactions in solution