Excess volumes of mixing of some binary aqueous organic mixtures up to 2.2 kbar.

Excess volumes of 2-butanol+water have been determined indirectly from temperatures 5° to 85 C at low pressure. VE for the same system has also been determined directly from 1° to 85°C at pressures up to 2. 2 kbar using a newly developed low-cost high pressure dilatometer. Excess volumes of ethanol +water and butanone+water have directly been determined at 25° and 50°C, and 30°C respectively. All three systems studied exhibit negative volume changes on mixing at and near ambient pressures. The alcohol+water mixtures having very low alcohol concentration show positive volume changes at extreme pressures. A similar tendency is found in butanone+water mixtures. The VE measurements of 2-butanol+water and ethanol+water have been shown to be consistent with whatever reliable volumetric and LLE data is available. Direct VE measurements of butanone+water are not in agreement with the only other available data (not very reliable). The ability of the UNIQUAC equation to describe the volumetric behaviour of 2-butanol+water was tested and as with expressions for excess Gibbs free energy, good VE fit and good phase equilibrium predictions make inconsistent demands on the values of the adjustable parameters. The high pressure dilatometer has also been used to deter mine compressions of pure water, 2-butanol, ethanol and butanone, and the results are found to be in agreement with the reliable available data. The Tait's and Huddleston's equations have been found to represent the compression data well, though the former seems to do it better than does the latter