An ionic liquid (IL), [C(4)Py][Al(2)Cl(7)] (n-butylpyridinium heptachlorodialuminate), was prepared, and its density and surface tension were measured under dry argon in the temperature range from (298.15 to 333.15) K. The experimental data showed that the Eotvos equation was applicable to the IL and the experimental parachor value was larger than that calculated from neutral parachor contribution which did not consider the Coulomb interaction in IL. In terms of Glasser's theory, the molar entropy, S(0), and the lattice energy, U(POT) were estimated. Using Kabo's method the molar enthalpy of vaporization Delta(8)(1)H(m)(0) (298 K) and using the interstice model the thermal expansion coefficient, alpha, for [C(4)Py][Al(2)Cl(7)] were predicted, respectively.