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

The recently proposed model [Geochim. Cosmochim. Acta 64 (2000) 495; Geochi m. Cosmochim. Acta 64 (2000) 2779] for correlating the infinite dilution pa rtial molar properties of aqueous nonelectrolytes is briefly outlined. The approach is fundamentally based on the A(12) = V-2(0)/kappa RT Parameter, r elated to the infinite dilute solute-water direct correlation function inte gral. The A12 parameter is considered as a semiempirical function of temper ature and density. At supercritical temperatures thermodynamic integrations of this function allow calculation of all thermodynamic functions of hydra tion (V-2(0), Delta (h)G(0), Delta H-h(0) and Delta hC(p)(0)) of a solute. An extension to subcritical conditions is done using an auxiliary Delta C-h (p)0(T, P-r)-function, which describes the temperature course of the heat c apacity of hydration of a solute at P-r = 28 MPa and subcritical temperatur es. The variations of the Delta C-h(p)0(T, Pr)-function are constrained by known values of Delta hG(0), Delta H-h(0) and Delta C-h(p)0 at ambient and supercritical conditions. This model, which was used earlier to correlate p roperties of a few dissolved gases, is successfully employed here to descri be V-2(0), Delta (h)G(0), Delta H-h(0) and Delta C-h(p)0 experimental resul ts for a number of aqueous nonelectrolytes, including ones of high polarity (alcohols, amines, acids and amides) and/or large size (hexane and benzene ). (C) 2001 Elsevier Science B.V. (C) All rights reserved.