Salt Effect in Vapor-Liquid Equilibria

Abstract

Vapor-liquid equilibrium data at atmospheric pressure were obtained for the methanol-water system containing sodium chloride, calcium chloride, or aluminium chloride of various concentrations and for the water-acetic acid system containing sodium chloride, sodium nitrate, or magnesium chloride of various concentrations.
The water-acetic acid system containing sodium chloride has an azeotrope above a certain concentration of the salt, and the composition becomes richer in acetic acid with increasing salt concentrations.
The relative volatility of the water-acetic acid system reverses its trend, that is, acetic acid becomes more volatile than water by the addition of magnesium chloride above a certain concentration.
For the representation of the salt effect a simple empirical equation is proposed, which correlates the data for the water-acetic acid system very well but does not fit the data for the methanol-water system. The data for the latter system can be correlated by the equation proposed by Johnson et al.