Vapor‐liquid equilibrium in alcohol‐water systems containing dissolved halide salts and salt mixtures

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Abstract
Isobaric vapor‐liquid equilibrium data at atmospheric pressure are reported for 17 systems, each consisting of water, an alchol (methanol or ethanol), and either a salt or a mixed pair of salts having a common anion, dissolved to saturation in the boiling liquid phase. The matris of four salts employed consisted of the sodium and potassium bromides and iodides. Solubility data are reported in terms of saturation salt concentration as a function of alcohol‐water proportionality in the liquid.Some of these salts and salt mixtures were found capable of eliminating the ethanol‐water azeotrope completely. Relative volatility was observed to be enhanced by as much as threefold in certain cases. Orders of effectiveness of both the cations and anions were in agreement with those observed by previous investigators of the effects of electroytes in mixed solvents. The value of the salt effect parameter was observed to undergo major variation as a function of alcohol‐water mixed solvent proportionality in the methanol‐water‐salt systems, but to be remarkably constant throught the ethanol‐water‐salt systems. Synergistic effects of mixed salts on vapor‐liquid equilibrium were observed in certain systems despite their apparent lack in the corresponding salt solubility relationships. In systems where synergistic effects did exist they were found to be dependent stronly on liquid composition, largely lacking in water‐rich regions, and evident only in midrange and alcohol‐rich regions of binary solvent composition. In some of these systems the salt appeared to cause both salting out and salting in of the alcohol in differing composition regions of the same system, the predominating effect depending on the relative proportions of alcohol and water present. This latter effect is in general contradiction with the accepted theories of salt effect in vapor‐liquid equilibrium.

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