Solvation thermodynamics of gas solubility at sub‐ and near‐critical conditions

Solvation phenomena in dilute multicomponent solutions I. Formal results and molecular outlook

“…2 The controversy was significantly eased after the development of a rigorous solvation formalism for the unambiguous identification and isolation of the contributions from the two length scales in infinitely dilute solutions. [3][4][5][6] Unfortunately, while the solubility of volatile and nonvolatile species in highly compressible solvent is significantly low but usually much larger than the corresponding ideal gas counterparts, the actual systems are never at infinite dilution, i.e., we must deal with the changing composition and its effect on the phase behavior ͑structure and stability͒.…”

“…This is a natural choice in that the systems of interest are dilute solutions, whose properties can be obtained from suitable free energy composition expansions, based on fugacity or activity coefficients 20,21 around the infinite dilution reference, for which we have at our disposal a rigorous solvation formalism for the characterization of the reference system. [3][4][5][6]8,22 In fact, we have successfully portrayed the solvation process of infinite dilute solutes in any solvent medium and in compressible solvents, in particular, in terms of the solvent's local density perturbation caused by the presence of a solute molecule, and the concomitant propagation of this perturbation a distance given by the system's correlation length. 1,3,8 Moreover, to make contact between the above microscopic picture and the resulting macroscopic ͑thermo-physical͒ properties of interest, we have invoked the unambiguous separation between direct and indirect correlation functions via the Ornstein-Zernike equation.…”

Solvation effect on kinetic rate constant of reactions in supercritical solvents

“…the superscripts IG denote ideal gas properties, and the solvation contribution to the partial molar volumes Pr(SR) can be interpreted microscopically in terms of either total or direct correlation function integrals, as discussed in detail in Cummings, 1994, 1995;Chialvo et al. 1996) and summarized in Appendix A.…”

“…This behavior can be clearly seen in Figures 3 and 4, where we display the corresponding density dependence for ( d P / % X . p , X k " ) the macroscopic quantity that most succinctly characterizes the solvation phenomenon Cummings, 1994, 1995;Chialvo et al 1996).…”

“…To make contact with the microstructure of the system we express (dP/dx,)", p, xi in terms of total pair correlation function integrals (TPCFI), or alternatively, in terms of direct pair correlation function integrals (DPCFI) as follows (Chialvo and Cummings, 1994;Chialvo et al, 1996), so that, the short-range portion of the species partial molar volume at infinite dilution becomes Now, if the solvent becomes an ideal gas, that is, K + K '~ and p + ( P / k T ) , then Eqs. A14-A16 reduce to and The expressions Eqs.…”