Excess molar volumes of aqueous solutions of butylamine isomers

Excess molar volumes (V-E) and average thermal expansivities (alpha) of the systems, water (W) + n-butylamine (NBA), W + sec-butylamine (SBA), and W tert-butylamine (TBA), have been calculated from the density data at tempe ratures ranging from 298.15-323.15 K. The V-E and alpha values have been pl otted as functions of mole fraction of amines. The systems show large negat ive excess volumes, magnitude of which varies in the order, W + TEA > W + S EA > W + NEA. The curves are found to be symmetrical along the composition axis, with minima occurring at 0.5 mole fraction of butylamines. The negati ve excess volumes have been interpreted primarily by two effects: (i) stron g chemical interaction leading to the formation of 1:1 complexes through H- bonding and (ii) hydrophobic hydration causing significant contraction of v olume.