Surface tension of esters. Temperature dependence of the influence parameter in density gradient theory with Peng-Robinson equation of state

A new temperature-dependent correlation for the reduced influence parameter of the density gradient theory, when used with the Peng-Robinson equation of state, is proposed and compared with other correlations found in the literature. The proposed correlation is linear in its two fitting parameters and contains a universal exponent related to the one from the liquid-vapor phase transition universal scale law. The overall absolute deviation (OAAD) respect 1275 surface tension data for 39 esters is 1.37%. Only the proposal from Zuo and Stenby with OAAD = 1.29%, yields similar results with the same number of parameters. Fitting parameters for the new correlation proposed and those from Zuo and Stenby are given for the fluids considered in this work.