An extended scaled equation for the temperature dependence of the surface tension of pure compounds inferred from an analysis of experimental data

We have made a literature survey and performed a critical analysis of the available experimental surface tension data for the most volatile compounds in petroleum fluids: nitrogen, methane, ethane, propane, i-butane, n-butane, n-pentane, n-hexane, n-heptane and n-octane. Including the selected data with those for oxygen, xenon, krypton and those obtained recently for 16 partially halogenated hydrocarbons (refrigerants), we propose the following extended scaled equation to represent the surface tension of these substances:σ=kTcNAVc2/3(4.35+4.14ω)t1.26(1+0.19t0.5−0.25t)where t1−T/Tc is reduced temperature, k, NA, Vc, and ω are the Boltzmann constant, Avogadro number, the critical volume and the acentric factor, respectively. This equation, which only differs slightly from that proposed by Schmidt et al. [J.W. Schmidt, E. Carrillo-Nava, M.R. Moldover, Fluid Phase Equilibria 122 (1996) 187–206] for refrigerants, yields values for σ within 3.5% of the experimental values for all these compounds. Available data for other compounds (refrigerants) are in agreement with this relation; in the light of that we also examine some compounds (carbon dioxide and argon) for which there exist conflicting datasets.