Partial Molar Volumes in Aqueous Mixtures of Nonelectrolytes. I. <i>t</i>-Butyl Alcohol

Abstract

Abstract The densities of mixtures of t-butyl alcohol (TBA) with water (W) have been measured at various temperatures over a wide range of concentrations. From these data the apparent (VΦ,2) and partial (V2) molar volumes as well as partial molar expansibilities (E2) have been evaluated for both components. The limiting partial molar volumes, VTBA∞ and VW∞, were smaller than the molar volume of TBA and water, respectively, at all temperatures studied. The values of ETBA∞ was negative at temperatures below 15 °C and the value of EW was also negative at all temperatures. Characteristic extrema were observed for the VTBA(XTBA) and ETBA(XTBA) curves in the water-rich region and for the VW(XW) curve in the TBA-rich region. The unusual volumetric behavior found for the TBA–water mixtures at both ends of the composition may be attributed to the formation of strong hydrogen bonding between water and TBA molecules and to the unique properties of pure water, itself (i.e., the very small size of water molecules and the existence of a cluster structure).