Partial molal enthalpies,excess partial molal heat capacities,and structural effects ofn-Am4NBr in the water-dioxane system

Integral heats of solution of tetra-n-pentylammonium bromide, n-Am₄NBr, in aqueous binary mixtures of dioxane are reported at 25° and 35°C from 0.0 to 0.3 mole fraction of dioxane. The excess partial molal heat capacity c_p^° at 30°C is derived from the integral heats of solution at infinite dilution at 25° and 35°C. The partial molal enthalpies of n-Am₄NBr exhibit a rather flat maxima at 0.2 mole fraction dioxane. The c_p^° values suggest a structure-breaking role for dioxane. The results obtained in this study are compared with those obtained with n-Bu₄NBr in the same system in an earlier study.