Second Cross Virial Coefficients for Interactions Involving Water. Correlations and Group Contribution Values

A simple method is presented for estimating the second cross virial coefficients for interactions involving water. It is based on the Tsonopoulos corresponding-states correlation and consists of a semiempirical equation for evaluating the mixture-specific parameter k ₁₂ of this correlation. The general structure of this equation is guided by a theory-based relation, which is valid for interactions between spherical nonpolar molecules. An empirical extension of this relation to interactions involving water was done by replacing the "energy" term with a function of the Gibbs energy of hydration of a compound at 298 K and 0.1 MPa. This correlation is supported by experimental B ₁₂ values for interactions between water and numerous compounds that differ greatly in size and strength of water-solute interactions. Limitations of this empirical correlation are briefly discussed. In addition, available B ₁₂ data for interactions between water and normal alkanes, from ethane to octane, strongly suggest the applicability of a group contribution method to predict the second cross virial coefficients between water and organic compounds. For interactions between water and large organic molecules, the group contribution approximation is the method of choice for B ₁₂ predictions. These findings were employed to predict the B ₁₂ values from (275 to 1200) K for interactions between water and many inorganic and small organic compounds (halogenated derivatives of methane and ethene), as well as for many functional groups of organic compounds.