Headspace gas chromatographic measurements of limiting activity coefficients of eleven alkanes in organic solvents at 25 °C. 1

In the present study we report the infinite dilution activity coefficients (gamma(infinity)) of 11 alkanes in 67 organic liquids at 25 degrees C measured by fully automated headspace gas chromatography. This study is part of a more comprehensive one whose main objective is to compare the predictive ability of several semitheoretical models to estimate alkane gamma(infinity) values. To do this it is obviously necessary to collect reliable experimental data spanning a wide range of chemical properties. The solutes include five linear (pentane to nonane), four branched (2-methylpentane, 2,4-dimethylpentane, 2,5-dimethylhexane, 2,3,4-trimethylpentane), and two cyclic (cyclohexane and ethylcyclohexane) alkanes. The solvents include several homologous series: n-alkanes, 1-alkenes, n-alcohols, 2-ketones, nitriles, acetates, and 34 other common volatile and nonvolatile solvents. Several modifications introduced to the previously reported instrumentation and to the quantitation method are discussed. The data presented are the average of at least two independent measurements with a precision better than 5%.