Liquid Equilibria in Aqueous Solutions

We next consider the equilibrium or solubility of a vapor in aqueous solution. The equilibrium can be represented as  

The activity of a vapor species can be expressed, analogous to aqueous species, by the form 

Once again, we have a coefficient which captures the nonideality in terms of temperature, pressure and composition effects. Combining (3.19) and (3.20) we get 

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Conclusions The correlation of vapor-liquid equilibria in aqueous solutions of weak electrolytes is important for the separation of undesirable components from gases and liquids. The major problem in such correlations is the estimation of the activity... 

Sander, B., Rasmussen, P. and Fredenslund, A. Chem. Eng. Sci. 41 (1986) 1197-1202. Calculation of solid-liquid equilibria in aqueous solutions of nitrate salts using an extended uniquac equation. 

Edwards et al. (1975, 1978A, B) established a molecular-thermodynamic correlation for calculating vapor-liquid equilibria in aqueous solutions containing one or more volatile electrolytes, with special attention to the ternary systems, ammonia-carbon dioxide-water and ammonia-hydrogen sulfide-water. Their 1978 correlation was shown to give results in satisfactory agreement with the limited data then available for temperatures from 0° to 170°C (32° to 338° F) and ionic strengths of about 6 molal (equivalent to total concentrations of the electrolytes between 10 and 20 molal). 

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