Semiempirical equation of state for the infinite dilution thermodynamic functions of hydration of nonelectrolytes over wide ranges of temperature and pressure

A. V. Plyasunov, J. P. O'Connell, R. H. Wood, Everett Shock

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The recently proposed model [Geochim. Cosmochim. Acta 64 (2000) 495; Geochim. Cosmochim. Acta 64 (2000) 2779] for correlating the infinite dilution partial molar properties of aqueous nonelectrolytes is briefly outlined. The approach is fundamentally based on the A12 = V2 0/κRT parameter, related to the infinite dilute solute-water direct correlation function integral. The A12 parameter is considered as a semiempirical function of temperature and density. At supercritical temperatures thermodynamic integrations of this function allow calculation of all thermodynamic functions of hydration (V2 0, ΔhG0, ΔhH0 and ΔhCp 0) of a solute. An extension to subcritical conditions is done using an auxiliary ΔhCp 0(T, Pr)-function, which describes the temperature course of the heat capacity of hydration of a solute at Pr = 28 MPa and subcritical temperatures. The variations of the ΔhCp 0(T, Pr)-function are constrained by known values of ΔhG0, ΔhH0 and ΔhCp 0 at ambient and supercritical conditions. This model, which was used earlier to correlate properties of a few dissolved gases, is successfully employed here to describe V2 0, ΔhG0, ΔhH0 and ΔhCp 0 experimental results for a number of aqueous nonelectrolytes, including ones of high polarity (alcohols, amines, acids and amides) and/or large size (hexane and benzene).

Original languageEnglish (US)
Pages (from-to)133-142
Number of pages10
JournalFluid Phase Equilibria
Publication statusPublished - Jul 1 2001
Externally publishedYes



  • Chemical potential
  • Enthalpy
  • Equation of state
  • Fugacity
  • Gibbs energy
  • Heat capacity
  • Model
  • Volume

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes
  • Physical and Theoretical Chemistry

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