Surface tension prediction for pure fluids

For the surface tension of organic compounds, sigma = [P .(rho(l) - rho(tau)](4) is proposed where P = P-0 .(1 - T-r)(0.37). T-r . exp(0.30066/T-r + 0.86442 . T-r(9)). rho(l) and rho(nu) are molar densities of liquid and vapor, respectively, T-r = T/T-c, and P-0 is a temperature-independent, compound-dependent constant similar to Sugden's parachor. This new expression, derived from statistical-mechanics, represents the experimental surface tension data of 94 different organic compounds within 1.05 AAD%. We also propose P-0 = 39.6431 .[0.22217 - 2.91042 x 10(-3).(R*/T-br(2)). T-c(13/12)/P-c(5/6) as a corresponding-status expression to correlate the temperature-independent parameter P-0 for various compounds. Here, R* + R(m)/R(m,ref), R(m) is the molar refraction, R(m,ref) is the molar refraction of the reference fluid (methane), and T-br is the reduced normal boiling point. When this generalized expression is used, surface tensions for all 94 compounds can be predicted within 2.57 AAD% at all temperatures investigated.