Osmotic and activity coefficients in the binary solutions of 1-butyl-3-methylimidazolium chloride and bromide in methanol or ethanol at T = 298.15 K from isopiestic measurements

Osmotic coefficients of the binary solutions of two room-temperature ionic liquids (1-butyl-3-methylimidazolium chloride and bromide) in methanol and ethanol have been measured at T = 298.15 K by the isopiestic method. The experimental osmotic coefficient data have been correlated using a forth-order polynomial in terms of (molality)0.5, with both, ion interaction model of Pitzer and electrolyte non-random two liquid (e-NRTL) model of Chen. The values of vapor pressures of above-mentioned solutions have been calculated from the osmotic coefficients. The model parameters fitted to the experimental osmotic coefficients have been used for prediction of the mean ionic activity coefficients of those ionic liquids in methanol and ethanol.

► The osmotic coefficients of the solutions of 1-butyl-3-methylimidazolium chloride and bromide in ethanol and methanol have been measured.
► Measured osmotic coefficients were correlated using NRTL and Pitzer models.
► Vapor pressures were evaluated from the correlated osmotic coefficients.
► Model parameters have been interpreted in terms of ion–ion and ion–solvent interactions.