In this paper a group contribution method is applied to determine surface tension of pure ionic liquids. The critical properties (Tc, Pc and Vc), the normal boiling point temperature (Tb), the critical compressibility factor (Zc), and the density (ρ) of pure component are necessary inputs for this prediction. Surface tension for a series of ten ionic liquids (ILs) 1-alkyl-3-methyl-imidazolium bis (trifluoromethanesulfonyl) imide [Cnmim][NTf2], with the alkyl chain length n = 2, 3, 4, 5 and 6 at different temperature were determined. The average relative error obtained from the comparison of experimental and calculated surface tension values for studied ionic liquids show, the model has good accuracy in comparison with other predictive equations
