The effect of organic electrolytes Me4NBr, Et4NBr, Pr4NBr, Bu4NBr, Me4NCl and Me4NI on the aggregation behavior and thermodynamic properties of surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) in aqueous solution was studied by volumetric, compressibility and conductometric measurements at different temperatures. The results show that all the electrolytes investigated effectively reduce critical micelle concentration and therefore have a salting-out effect on the aggregation of [C12mim]Br in aqueous solutions. It was also found that the salting-out-inducing anions are predominately responsible for the observed effect, while the cations have a very smaller effect on the salting-out strength. The ability of the anions to promote the aggregation of SAIL decreases in the order of I− N Br− N Cl−; however all the investigated cations Me4N+, Et4N+, Pr4N+ and Bu4N+ have a similar salting-out strength. Changes in the apparent molar volumes and isentropic compressibilities upon micellization were derived and the infinite dilution apparent molar properties of the monomer form of [C12mim]Br were determined. Furthermore the effect of electrolyte on the degree of anionic binding and the thermodynamic parameters of aggregation for [C12mim]Br in aqueous solutions were determined.
