Vapor pressure measurements of ethanol–isooctane and 1-butanol–isooctane systems using a new ebulliometer

A new, simpler ebulliometer has been developed to accurately measure the vapor pressure of ethanol–isooctane and 1-butanol–isooctane systems at various mixture compositions. The reliability of the experimental apparatus was validated by comparing the experimental data with published data for pure isooctane and ethanol and ethanol–isooctane system. Our data were in good agreement with the published data, with a deviation of less than 1.9%. The vapor pressure of an ethanol–isooctane mixture was initially elevated by the addition of ethanol until the ethanol concentration reached 0.3 mass fractions, then dropped at concentrations above 0.7 mass fractions. For a 1-butanol–isooctane system, the vapor pressure decreased with increasing 1-butanol concentrations. The experimental data were correlated using the Wilson, Non-Random Two-Liquid (NRTL), and Universal Quasi-Chemical (UNIQUAC) activity coefficient models with an average absolute deviation in the vapor pressures of 3.5%, 3.3%, and 6.1%, respectively.