Sound speed and density measurements for tetra- n-butylammonium bromide in benzene and carbon tetrachloride solutions at T = 298.15 K

Abstract

The density and sound speed measurements have been carried out for the binary systems consisting of tetra- n-butylammonium bromide (Bu 4NBr) as a solute in benzene and CCl 4 at T = 298.15 K (concentration range 0.01 mol · kg −1 to ∼0.8 mol · kg −1). The apparent molar volumes ( ϕ V) and apparent molar isentropic compressibility ( ϕ K S ) have been calculated and the values at infinite dilution are estimated. These data for Bu 4NBr in benzene and CCl 4 solutions are combined with the literature data of Bu 4NBr in water to obtain transfer compressibility of Bu 4NBr molecules from non-aqueous to aqueous solutions. The ϕ V behaviour as a function of concentration in benzene solutions indicates formation of reverse micelles and having critical micelle concentration (cmc) around 0.01 x 2 of Bu 4NBr (∼0.13 mol · kg −1). The compressibility data are further used to estimate hydration number of Bu 4NBr in aqueous solutions by applying Shiio’s method. The hydration number calculated for compressible organic electrolyte shows good agreement with the number obtained for clathrate hydrate of Bu 4NBr using the chemical analysis and X-ray diffraction.