Equilibrium properties are represented by sum of molar-additive quantities expressed through component#s properties, and surplus properties determined as a power number according to Redlich-Kister equation. A number of permanent coefficients in addends is determined by modulus average minimum of absolute deviation of both calculation and experiment equilibrium property value. Equations for general vapour pressure of non-ideal solutions, boiling temperature, vapour structure, temperature of hard solution crystallization, chemical equilibrium constant of different stoichiometry are composed.