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-propanoland water. The VLE experiments were performed using a modified Othmer still a t ambient pressure. The effect of salt on the relative volatility 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-out behavior of the alcohol was observed. The azeotrope was shifted but apparently not eliminated for the salt concentrations studied. Density measurements at 25,40, and 55 "C were taken using a vibrating tube densimeter at four salt molalities over the full range of solvent 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 ternary mixture.