I. The Basis of the Thermodynamic Description of Non-Electrolyte Solutions. Introduction. Basic thermodynamic relationships. Equilibrium conditions at constant temperature and pressure. Conditions for thermodynamic stability and the critical point. The nonclassical behaviour of systems in the critical region. Empirical and semi-empirical equations for the concentration dependence of the Gibbs energy. The dependence of the excess Gibbs energy on temperature. II. Liquid-Liquid Equilibria in Binary Systems. The shape of the equilibrium curve (liquid-liquid equilibrium) for binary systems. Description of the behaviour of binary systems using the relationship for a strictly regular solution. Calculation of the compositions of coexisting phases in a binary system. Calculation of the parameters of the empirical relationships for the excess Gibbs energy for heterogeneous systems. Parameter calculation in empirical relationships for the Gibbs energy for homogeneous binary systems. III. Liquid-Liquid Equilibria in Ternary and Multi-Component Systems. The shape of the equilibrium curve (envelope) in ternary and quaternary systems. The concentration dependence of the excess Gibbs energy for multi-component systems. Modelling of liquid-liquid equilibria in ternary systems. Calculation of the compositions of coexisting phases in multi-component systems. Calculation of the critical point. Calculation of the parameters in the empirical relationships for the excess Gibbs energy from data on liquid-liquid equilibria in ternary systems. Prediction of liquid-liquid equilibria and empirical relationships used to describe liquid-liquid equilibria in ternary systems. Experimental determination of liquid-liquid equilibria. Appendices. References. Index.