Backone family of equations of state: 2. Nonpolar and polar fluid mixtures

In the BACKONE equations the Helmholtz energy F is written as the sum F = FH + FA + FD + FQ, where FH is the hard‐body contribution, FA the attractive dispersion force contribution, FD the dipolar, and FQ the quadrupolar contribution. In Part 1 of this article (Müller et al., 1996a) the construction of BACKONE and its application to pure fluids were presented. In the extension to mixtures, for each term of F a specific mixing rule is used. This concept requires only one adjustable state‐independent binary mixture parameter. To demonstrate the feasibility of this approach, predictions of phase equilibria, including a liquid–liquid equilibrium and other thermodynamic properties, are given for 20 binary fluid mixtures from the groups: nonpolar + nonpolar; nonpolar + dipolar; nonpolar + quadrupolar; and polar + polar.