Determination of Isobaric Vapor–Liquid Equilibria Data for Four Alcohol+Water Binary Systems at Low Alcohol Mole Fractions 10⁻⁶ to 10⁻²

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Information on vapor–liquid equilibria in the extremely dilute regions is necessary for developing high-grade purification processes. In this study, we examine the vapor–liquid equilibria (x–y–T–P) of liquids containing 1×10⁻⁶ to 1×10⁻² mole fractions of alcohols for four binary systems, i.e., methanol+water, ethanol+water, 2-propanol+water, and 2-methyl-2-propanol+water, at 101.325 kPa using two Rose–Williams stills with a special device for a sampling system. The infinite-dilution equilibrium ratios K₁^∞ were measured, and the infinite-dilution activity coefficients obtained from K₁^∞ were compared with the literature and predicted values using modified UNIFAC (Dortmund) and ASOG. The x–y–T–P data at the finite composition regions were then calculated using Wilson parameters obtained by the infinite-dilution activity coefficients.