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

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 A 12 = V 0 2 /κRT parameter, related to the infinite dilute solute-water direct correlation function integral. The A 12 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 (V 0 2 , Δ h G 0 , Δ h H 0 and Δ h C 0 p ) of a solute. An extension to subcritical conditions is done using an auxiliary Δ h C 0 p (T, P r )-function, which describes the temperature course of the heat capacity of hydration of a solute at P r = 28 MPa and subcritical temperatures. The variations of the Δ h C 0 p (T, P r )-function are constrained by known values of Δ h G 0 , Δ h H 0 and Δ h C 0 p 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 V 0 2 , Δ h G 0 . Δ h H 0 and Δ h C 0 p 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).

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