Excess Magnitudes for Ionic Liquid Binary Mixtures with a Common Ion

Densities, isobaric thermal expansivities, and excess enthalpies were determined for the binary systems formed by ionic liquids with a common anion, 1-hexyl-3-methylimidazolium tetrafluoroborate + 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium tetrafluoroborate + 1-butyl-3-methylimidazolium tetrafluoroborate, and by those with a common cation, 1-butyl-3-methylimidazolium tetrafluoroborate + 1-butyl-3-methylimidazolium methylsulfate and 1-butyl-3-methylimidazolium tetrafluoroborate + 1-butyl-3-methylimidazolium hexafluorophosphate. Volumetric properties were obtained by means of a vibrating tube densimeter, whereas Calvet microcalorimetry was used to determine the excess enthalpies. Due to the high viscosity of the samples, nonstandard experimental techniques had to be used to obtain the results. The experimental data are interpreted on the basis of the chemical structure of the ionic liquids.