Apparent Molar Volumes of Benzyltrimethylammonium Bromide and Its Homologs in Aqueous Solution at 15, 25, and 35°C

Apparent molar volumes at infinite dilution of benzyltrimethylammonium bromide and its butyl and hexyl homologs at 15, 25, and 35°C and of dibenzyldimethylammonium bromide at 25°C in aqueous solution were estimated from density measurements. The additivity rule for the contribution of the methylene groups to the apparent molar volumes was found to be obeyed within a broad range of homologs, which covers the parent salt and the dodecyldimethylbenzylammonium bromide. The volumetric contribution of the phenylene (–C₆H₄–) group was estimated to be 61 cm³-mol^–1 at 25°C. A value of –16.9 ± 0.3 cm³-mol^–1 was suggested for the volumetric contribution of the N⁺ fragment to the apparent molar volume of alkylbenzyldimethylammonium salts.