Maximum Partial Area Rule for Phase Equilibrium Calculations

Eubank and Hall have shown recently that the tangent-line criterion reduces to an equal area construction for the derivative of the total Gibbs energy plotted against composition. This paper presents another criterion along with a thermodynamic proof, the maximum partial area rule (MPAR), which establishes an area on the plot of the derivative of the Gibbs energy with respect to composition which is always a maximum at equilibrium. The method based upon this criterion is especially powerful for complex phase equilibria involving multiple components and phases.