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Waring and Riedel Functions for the Liquid–Vapor Coexistence Curve
journal contribution
posted on 2012-02-22, 00:00 authored by Santiago Velasco, Juan A. White, Kandadai Srinivasan, Pradip DuttaThere exists a minimum in the Waring function, ψ(T) = −d(ln p)/d(1/T), and in the Riedel function, α(T) = d(ln p)/d(ln T), in the liquid–vapor
coexistence curve for most fluids. By analyzing National Institute
of Standards and Technology data for the molar enthalpy of vaporization
and the compressibility variation at the liquid–vapor phase
change of 105 fluids, we find that the temperatures of these minima
are linearly correlated with the critical temperature, Tc. Using reduced coordinates, we also
demonstrate that the minima are well-correlated with the acentric
factor. These correlations are used for testing four well-known vapor
pressure equations in the Pitzer corresponding states scheme.