Volumetric Properties of Alkyltrimethylammonium Bromides in Aqueous Solutions
Density data of good precision for binary aqueous solutions containing salt of a homologous series of alkyltrimethylammonium bromides [hexyl (C6TAB) octyl (C8TAB) decyl (C10TAB) dodecyl (C12TAB) tetradecyl (C14TAB) and hexadecyl (C16TAB) at 293.15, 298.15, and 303.15 K are reported. Using the density data, the apparent molar volumes of solutes at finite concentration (phV) and at infinitely dilute solutions (phV0) have been calculated. The partial molar volumes (V2) apparent molar expansivity (phE) and limiting molar expansivity (phE0) parameters at 298.15 K are also reported. The pseudophase separation model has been utilized to estimate critical micelle concentration (cmc) and aggregation number (n) of the studied surfactant molecules. The main result of our studies is the observation that the expansivity parameter goes through a maximum at cmc except in the case of C6TAB and C8TAB surfactants at 298.15 K. The volume changes due to micellization (DVxmic) and standard unitary free energy changes for