On the Thermodynamics of Solutions. VII. Critical Properties of Mixtures

Abstract

The applicability of equations of state has been greatly widened by automatic computation. Algebraic relations, however, particularly strict thermodynamic relations, are apt to simplify the calculations and therefore to extend the applications much further. Explicit general relations between temperature, pressure and composition at the critical line of a binary mixture would be useful and also theoretically interesting. Although the problem is easily formulated, it appears that a general solution cannot be found. But a partial solution can be derived: The derivatives of the variables of state along the critical line in the limits of the critical points of the pure components can be expressed by partial derivatives in these points. The volume of a mixture increases on condensation in the range of retrograde condensation. This result may have been suspected on the basis of the principle of Braun and Le Chatelier.