Activity coefficients of C4–C8 n-alkanes in C16–C32 n-alkanes

Abstract

The activity coefficients at infinite dilution of C₄-C₇ n-alkanes in n-hexadecane at 30°C, n-eicosane at 40°C, n-docosane at 50 and 60°C and n-octacosane at 70°C have been determined by gas-liquid chromatography (G.L.C.) Mixed second virial coefficients (B₁₂) have been obtained for n-alkane + nitrogen carrier gas mixtures.

The activity coefficients have been discussed in terms of the lattice theory and the interaction parameters in terms of “end-group-middle-group” interactions using both segment and contact point treatments. The activity coefficients have also been discussed in terms of the Flory, Orwoll and Vrij theory and the Prigogine cell model. The agreement between experiment and the Flory et al. theory is reasonably good. The Prigogine cell model gives reasonable agreement with the experimental activity coefficient values but the agreement is poor for other excess properties. It is concluded that the lattice theory, despite its failures probably gives the most reasonable explanation of the deviations from ideality for n-alkane mixtures provided it is applied to constant volume conditions.