CHAPTER 9. Partial Molar Volumes of Gases Dissolved in Liquids

Abstract

The solubility of gases in liquids is a sub-discipline of vapour (V)–liquid (L) phase equilibria, and in addition to its profound theoretical interest, this topic is also of importance in many areas of the applied sciences. Chapter 9 focuses first on the relevant thermodynamics governing the solubility of non-reactive gases in liquids, and indicates, in particular, the central role of partial molar volumes of dissolved gases in rigorous solubility data reduction involving Poynting integrals. Inevitably, pride of place will be given to the Henry fugacity h2,1(T,Pσ,1(T)) of solute 2 dissolved in solvent 1, at pressure Pσ,1(T), the vapour pressure of the pure liquid solvent. This quantity is also known as Henry's law constant, and various popular approximations (involving partial molar volumes of the solute) concerning its relation to experimentally obtained solubility data, such as the Krichevsky–Kasarnovsky equation, will be discussed. Experimental techniques for the determination of VL∞2 will be presented, with the emphasis being placed on vibrating-tube densimetry. However, compared to the large body of data on gas solubilities, experimental results on VL∞2 (and on VL2 in general) of gases dissolved in liquids are not plentiful. Thus, a survey of current estimation techniques for indispensable auxiliary quantities, such as partial molar volumes at infinite dilution (and virial coefficients), will be included. Besides empirical methods, molecular-based approaches, such as scaled particle theory, will also be discussed.