Henry's law constants and infinite dilution activity coefficients of propane, propene, butane, 2-methylpropane, 1-butene, 2-methylpropene, trans-2-butene, cis-2-butene, 1,3-butadiene, dimethyl ether, chloroethane, and 1,1-difluoroethane in benzene, toluene, o-xylene, m-xylene, p-xylene, and styrene in the temperature range of (250 to 330) K were measured by a gas stripping method, and partial molar excess enthalpies and entropies were evaluated from the activity coefficients. A rigorous formula for evaluating the Henry's law constants from the gas stripping measurements was used for the data reduction of these highly volatile mixtures. The estimated uncertainties are about 2 % for the Henry's law constants and 3 % for the infinite dilution activity coefficients. The Henry's law constants followed the order of increasing Henry's law constant with decreases in the normal boiling point temperature of the liquefied gas except polar gases. In general, the partial molar excess enthalpies and entropies of gases in the aromatics increase with decreases of the polarities of the gases and increasing molecular size of the gases.