Density determination of binary mixtures containing ionic liquids using refractive index data

The density prediction for 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]) + ethyl acetate (EA) and butyl acetate (BA) binary mixtures were done from refractive index data in the entire range of compositions at 298.15 K . Experimental density and refractive index of pure components and refractive index of the binary mixtures were applied for the predictions. Also the refractive index prediction is possible from density and refractive index data of pure substances and from the experimental density of the mixtures. The method of prediction was based on the assuming ideal behavior of molar refraction. The Lorentz–Lorenz approximation was used in this method. Comparison of the predicted density values and experimental data for the mixtures were performed. The agreements between them were good. The results show that the assumption was accurate and acceptable data can be obtained. Since the measurement of refractive index is very simpler than density, the prediction method for density is very useful except where high accuracy is required.

Keywords:

ionic liquids , binary mixture , density , refractive index , Lorentz–Lorenz approximation