Thermodynamics of Binary Systems near the Liquid-Gas Critical Point

Abstract

The liquid-gas critical line in binary mixtures is discussed in terms of a theory based on the assumption that the phase transition may be described in terms of a single ordering field and an effective critical temperature. The theory, an application of a theory of Fisher to a case not considered by him, makes a number of predictions, among them that the specific heat at constant pressure and the isothermal compressibility, both at constant concentration, are weakly singular at the critical line. Azeotropic critical points, as well as points where either the critical pressure or critical temperature shows an extremum, are special cases in which the transition differs from that at a general point on the critical line. The theory is consistent with the few available experimental results.