A new air and water stable ionic liquid (IL) based on rhenium, N-butyl-pyridine perrhenate (([C4Py][ReO4]), was synthesized. The density and surface tension of the IL were determined over the temperature range of (293.15-343.15) K. In terms of the Glasser theory of IL and parachor, a series of physicochemical properties: molecular volume, standard entropy, surface tension, and molar enthalpy of vaporization were predicted, respectively. According to the interstice model, the thermal expansion coefficient of the IL was calculated and in comparison with experimental value, it is in good agreement by 3.92%. (c) 2010 Elsevier Ltd. All rights reserved.