There are two principal reasons for the great amount of experimental and theoretical work on the properties of liquid mixtures1. The first is that they provide one way of studying the physical forces acting between the two molecules of different species, and second for the study of mixtures, is the appearance of new phenomenon (interactions) which are not present in pure liquids. The most interesting of these are, new types of phase equilibrium2 which arise from the extra degree of freedom introduced by possibility of varying the properties of components.