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General conditions of collinearity at the phase boundaries of fluid mixtures

Authors

  • P. T. Eubank,

    Corresponding author
    1. Texas A&M University, Department of Chemical Engineering, College Station, TX 77843
    • Texas A&M University, Department of Chemical Engineering, College Station, TX 77843
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  • M. A. Barrufet

    1. Texas A&M University, Department of Chemical Engineering, College Station, TX 77843
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Abstract

The general collinearity conditions at phase boundaries for mixtures are proved by thermodynamic identities for density and for entropy as functions of temperature, pressure, and composition. In the case of density/temperature/pressure/composition collinearity is always found at the cricondentherm or any temperature extremum, whereas for entropy/temperature/pressure/composition collinearity is always found at the cricondenbar or any pressure extremum. Qualitative phase diagrams for a typical binary system are presented in accordance with the derived inequalities. Whether a particular slope, involving the above variables, from the homogeneous side of the phase boundary is greater or less than that from the heterogeneous side depends on location on the phase boundary with respect to cricondentherm, critical point, and cricondenbar.

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