Representation of binary equilibria
Material transfer - Ideal compartmentalized distillation

In this section we will only deal with binary liquid-vapour equilibria with an azeotrope; please refer to the articles in Chemical Thermodynamics. in this treatise for the study of simple binary equilibria.

A binary system of two substances A and B can be described by a three-dimensional diagram (molar or mass fraction, temperature, pressure). In practice, isobaric sections of this diagram are used: the temperature is plotted on the ordinate and the molar (or mass) fractions of A and B in the liquid and vapour phases on the abscissa (respectively X_A, X_B and Y_A, Y_B with X_A + X_B = 1 and Y_A + Y_B = 1). The curves obtained are the boiling and dew curves respectively.