An equation to calculate the actual methylene middle parameter as a function of temperature

Methylene middle parameter αCH2(γCH2)0.5, the product of the methylene group's cross-sectional area (αCH2) and the root square of its dispersive free energy (γCH2), is the key parameter to calculate the dispersive surface components of solids (γsd) using inverse gas chromatography (IGC) at different temperatures. The only method reported to calculate αCH2(γCH2)0.5 as a function of temperature is the Dorris-Gray method. However, the conventional values of αCH2(γCH2)0.5 calculated by the Dorris-Gray method depend heavily on theoretical aspects. This paper establishes a novel equation calculating the actual αCH2(γCH2)0.5 as a function of temperature using the latest and most accurate surface parameters of seven successive n-alkanes. The obtained actual αCH2(γCH2)0.5 values are slightly higher those of the conventional αCH2(γCH2)0.5. At 20 °C, the actual αCH2(γCH2)0.5 generates γsd values less than those generated using the conventional αCH2(γCH2)0.5 by ∼3%, and this reduction in calculated γsd values increases linearly to become ∼5% at 100 °C. Therefore, using the new actual αCH2(γCH2)0.5 seems to mitigate the discrepancy between the γsd values measured by IGC and those measured by the contact angle method.