Molecular thermodynamics of salt effect in vapor-liquid equilibrium of ethanol-water systems

Scaled particle theory was used to derive a general expression for the salt effect parameter, K, of isobaric vapor-liquid equilibrium for ethanol-wate r-1-1 type electrolytic systems, which appears in the Furter equation. This expression was essentially a sum of two terms: 1, the hard sphere interact ion term calculated by Masterton-Lee's equation, 2, the soft sphere interac tion term calculated by Y. Hu's molecular thermodynamical model, in which t he diameters of nacked ions were replaced by that of solvated ions, the sol vation coefficients (i.e., in the radio of the latter to the former) were t aken to be adjustable parameters, their magnitude implies the ionic solvati on rules. A correlation equation for the local dielectrical constant around central ions with liquid concentration was obtained by mapping out experim ental points. The calculated salt effect parameters of 9 ethanol-water-1-1 type electrolytic systems were in good agreement with the literature values within the wide range of liquid concentration. (C) 1999 Elsevier Science B .V. All rights reserved.