Effect of mixed dissolved solutes on the vapour liquid equilibrium of the ethanol-water system: prediction and experimental verification

Abstract

The isobaric vapour liquid equilibria for ethanol-water system containing an unsaturated amount of a mixture of mercuric and lithium chlorides and a mixture of mercuric and cupric chlorides were experimentally determined using a modified Othmer still. Both the systems exhibits salting-out of ethanol. The effect decreases with increasing system pressure or a class 3 solute according to the classification proposed in an earlier publication. Both the local volume fraction (modified Wilson model) and local molar fraction models (modified NRTL model) proposed by Tan predict the vapour composition of the two systems with a mean absolute error of about 0.02-0.216 and the bubble points with a mean absolute error of about 0.6-0.8°C. The predictive accuracy of the local volume fraction model is slightly better than that of the local moral fraction model. Coupled with the results of earlier works, the models are shown to predict adequately the effect of dissolved non-volatile solutes on the VLE of solvent systems regardless of the type of solvent components or the types, concentration and with this study the number of components of non-volatile solutes.