Surface tension prediction for pure fluids

For the surface tension of organic compounds, σ = [ 𝒫·(ρl ‐ ρv)]4 is proposed where 𝒫 = 𝒫0·(1 − Tr)0.37·Tr·exp(0.30066/Tr + 0.86442·T ). ρl and ρv are molar densities of liquid and vapor, respectively, Tr = T/Tc, and 𝒫0 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 𝒫0 = 39.6431· [0.22217 − 2.91042 × 10−3·(ℛ*/T )·T /P ] as a corresponding‐states expression to correlate the temperature‐independent parameter 𝒫0 for various compounds. Here, ℛ* = ℛm,ref, ℛm is the molar refraction, ℛm,ref is the molar refraction of the reference fluid (methane), and Tbr 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.