This paper reports that new ionic liquids (ILs) have been prepared by directly mixing the chloride of group III and 1-methyl-3-pentylimidazolium chloride (PMIC) with molar ratio 1/1 under dry argon atmosphere. The densities and surface tension of these ILs were determined at temperature range of 273.15 K to 343.15 +/- 0.1 K. The properties for the ionic liquids were discussed by interstice model and Glasser's theory. (c) 2006 Elsevier Ltd. All rights reserved.