A model-guided determination of Δdis G2 ∞ for slightly soluble gases in water using solubility data: From the solvent's freezing point to its critical point

Abstract

There is continuing interest in the description of the solubility of nonpolar gases in water over a wide range of temperatures. On one hand, the solubility data are used in many fields of science and technology; and on the other hand, simulation and theoretical calculations require experimental data to test their results and predictions. For these reasons it is important to have a means of calculating from the experimental solubility data the Gibbs energy of dissolution of gases (Δdis G 2 ∞ ) and Henry's constant (k H) over all the temperature range of existence of liquid water. Under ambient conditions it is relatively easy to relate Δdis G 2 ∞ and, hence, k H to the solubility data of nonpolar gases. However, this simple procedure becomes increasingly complicated as the temperature approaches the critical temperature of the solvent and it is necessary to make important corrections to obtain the thermodynamic quantities for the dissolution process. This difficulty can be resolved with a procedure that employs a perturbation method applied to a simple model solvent to guide the correct determination of k H and Δdis G 2 ∞ . We describe in this work an iterative calculation procedure whose correctness was validated with a thermodynamic relationship that uses only experimental data, hence it is model-free. Unfortunately this relationship can be applied only to a few systems due to its data requirements. The iterative procedure described in this work can be extended to higher pressures, p≅50 MPa above the solvent's vapor pressure, and also to gases dissolved in nonaqueous solvents.