A flow-mixing calorimeter has been used to measure the excess molar enthalpy H-m(E)(p(O)) of (carbon dioxide + dioxane)(g) and (propane + dioxane)(g) at standard atmospheric pressure (p(O)) = 0.101325 MPa over the temperature range T = (373.2 to 433.2) K. The measurements on (propane + dioxane) were fitted by using (1 - k(12)) = 0.85 in the combining rule epsilon(12) = (1 - k(12))(epsilon(11)epsilon(22))(1/2). This value was used to calculate H-m(E) for (carbon dioxide + dioxane) but the measured values were found to be less positive than predicted. The difference was attributed to quadrupole-quadrupole coupling energy and this was estimated by assuming a quasi-chemical model which, for the carbon dioxide-dioxane interaction, yielded a value of the equilibrium constant K-12(298.15 K) = 0.126 MPa-1 and an enthalpy of association Delta H-12 = -(8.4 +/- 2) kJ.mol(-1). Second virial cross-coefficients have been derived from the measurements.