A Volumetric Study of Aqueous Primary Alcohols as Functions of Concentration and Temperature

Density measurements of aqueous solutions of ethanol, 1-butanol, and 1-pentanol made in this laboratory along with those made for methanol, ethanol, and 1-propanol by Benson and Kiyohara form the basis for a volumetric analysis of solutes possessing both hydrophilic and hydrophobic regions as functions of both concentration and temperature. The extent of deviation of the modified volume function with mole ratio was shown to provide a quantitative measure of non-ideality. The deviations from ideality for dilute solutions are mediated by the solvated regions surrounding the hydrophobic region and are a function of the number of methylene groups. This region was shown to consist of water exhibiting a higher degree of hydrogen bonding than that of bulk water in accordance with previous studies. Moreover, the partial molar volume at infinite dilution for these primary alcohols is nearly a linear function of the number of methylene groups.