Headspace gas chromatography for measurement of infinite dilution activity coefficients of C4 alcohols in water

For environmental and other reasons, there is interest in determining values of infinite dilution activity coefficients (γ∞) of organic solutes in volatile solvents, particularly in water. Here, we present a detailed description of a headspace gas chromatograph recently constructed for the measurement of infinite dilution activity coefficients and report values of γ∞ for 1-butanol, 2-butanol, 2-methyl-1-propanol (iso-butanol) and 2-methyl-2-propanol (tert-butanol) in water at 298.15, 303.15 and 308.15 K respectively. Our results at 298.15 K compare favorably with previously reported γ∞ data for these compounds. There is no comparable data at 303.15 and 308.15 K. Also, from these data we compute the excess enthalpy at infinite dilution, HE∞, for these compounds in water. Comparisons with published data for HE∞ extrapolated from finite concentration show considerable discrepancies.