Apparent molar compressibilities of transfer of electrolytes from water to aqueous tert-butanol solutions

Abstract

The densities and sound velocities of the solutions of NaCl, Et₄NBr and Bu₄NBr in <em>tert-</em>butanol water mixtures (0 to 7 mol%) have been determined at 25°C. The apparent molar compressibilities of the salts-at infinite dilution (ϕ) have been computed from the concentration variation of ϕ_k for these mixtures. The transfer compressibilities of the electrolytes (<img src='http://www.niscair.res.in/jinfo/delta.gif' border=0>ϕ<img src='http://www.niscair.res.in/jinfo/equation49.gif' border=0>)_trans from water to aqueous <em>tert</em>- butanol solutions show a non-linear behaviour as a function of co-solvent concentration. The transfer function has been interpreted in terms of pair and higher order interactions between the electrolytes and the co-solvent. In the water-rich region, the observed large negative (<img src='http://www.niscair.res.in/jinfo/delta.gif' border=0>ϕ<img src='http://www.niscair.res.in/jinfo/equation49.gif' border=0>)_trans value in the case of Bu₄NBr implies the importance of water structural effects and hydrophobic interaction in these solutions.