Excess molar isobaric heats capacities C-P(E) Of the mixtures of {x 1,3-dioxane or 1,4-dioxane+(1-x) 2,2, 4-trimethylpentane, or tetrachloroethene, or benzene} were measured at 298.15 K. C-P(E) curves for both 2,2,4-trimethylpentane systems were 'W shaped' which was discussed previously by Patterson et al. The values of C-P(E) for both tetrachloroethene systems were positive and also that of 1,3-dioxane+benzene system was positive. The values of C-P(E) of 1,4-dioxane+benzene system changed the sign from positive to negative with increase of mole fraction of dioxane. 'W-shaped' C-P(E) for the 2,2,4-trimethylpentane systems suggests the existence of non-randomness ascribed to dipolar interaction.