Abstract: An ionic liquid (IL) has been prepared by directly mixing AlCl₃ and 1-methyl-3-butylimidazolium chloride (BMIC) with molar ratio 1/1 under dry argon atmosphere. The densities and surface tensions of the pure IL were determined in the temperature range of (278.2±0.1) to (343.2±0.1) K. The properties for the ionic liquid were discussed in terms of Glasser′s empirical model. The values of volume of anion AlCl₄^{- were obtained. The mean contribution of per methylene (CH₂) group to standard entropy of the IL is 35.2 J•K-1•mol-1 and is in good agreement with contribution of 35.1 J•K-1•mol-1 from [Cn-min][NTf₂]. The crystal energy of the IL is much lower than that of ionic solids, which is the main reason for the liquid state of the IL at room temperature. In addition, the interstice model was applied to calculate the thermal expansion coefficient of the IL, and the result agrees reasonably with the experimental value.}

Key words: Ionic liquid, Density, Surface tension, AlCl₃, Interstice model, Glasser′s theory