Abstract
A description of the thermodynamic properties in the critical region of a physical system is obtained from a scaled expression for the free-energy F(ρ, T). In general, a nonsymmetric coexistence curve is predicted, with the symmetric case (e.g., magnets) included as a special example. For fluids, deviations from symmetry give rise to an expression for the average density below the critical point nonlinear in the temperature near Tc (in contrast to the usual “law of rectilinear diameter”); these asymmetries also contribute to the discontinuity in the specific heat along the critical isochore. To lowest order, the formulation reduces to Widom’s homogeneous scaling; the classical equations of state of the van der Waals type are incorporated as a special case.

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