Thermodynamics of mixtures with strongly negative deviations from Raoult’s law. Part 8. Excess molar volumes at 298.15 K for 1-alkanol + isomeric amine (C6H15N) systems: Characterization in terms of the ERAS model

Excess molar volumes, VE, at 298.15 K and atmospheric pressure, over the entire composition range for binary mixtures of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with hexylamine (HxA) and of 1-propanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with triethylamine (TEA) are reported. They are calculated from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the whole mole fraction range, indicating strong interactions between unlike molecules. These interactions are stronger for the solutions with methanol or ethanol. The corresponding values of the molar excess enthalpies, HE, and of the molar excess internal energies confirm this point. imolar composition, VE values for the 1-alkanol + HxA systems behave similarly to those of other systems previously investigated such as 1-alkanol + dipropylamine (DPA), + dibutylamine, or + methyl butylamine. For these mixtures, the main contribution to the VE seems to be due to the interactional term. In contrast, packing effects are much more important in 1-alkanol + TEA mixtures. HE of the studied solutions are consistently described by the ERAS model. The ERAS parameters point out that the strongest interactions between unlike molecules are encountered in the solutions including methanol.