VAPOR-LIQUID-EQUILIBRIA AND SALT APPARENT MOLAR VOLUMES OF THE WATER PLUS 2-PROPANOL PLUS TETRABUTYLAMMONIUM BROMIDE SYSTEM

Vapor-liquid equilibrium and density measurements have been performed on 1.00-5.89 m tetrabutylammonium bromide (TBAB) in mixtures of 2-prop anol and water. The VLE experiments were performed using a modified Ot hmer still at ambient pressure. The effect of salt on the relative vol atility of 2-propanol was evaluated at molalities of 1.00, 1.79, and 5 .89 over the full range of solvent composition. At each salt molality, as the alcohol concentration increased, salting-in and then salting-o ut behavior of the alcohol was observed. The azeotrope was shifted but apparently not eliminated for the salt concentrations studied. Densit y measurements at 25, 40, and 55-degrees-C were taken using a vibratin g tube densimeter at four salt molalities over the full range of solve nt composition. As salt molality increases, the apparent molar volume of TBAB exhibits a minimum between 1 to 2 m TBAB in pure water, it is slightly larger and monotonically increases in pure 2-propanol, and it is larger yet, with a maximum at lower 2-propanol amounts, in the ter nary mixture.