Volumetric and Conductance Studies of Cetyltrimethyl Ammonium Bromide in Aqueous Glycine

Abstract

Apparent molar volumes (ϕv), apparent molar adiabatic compressions (ϕκ) and thermodynamic parameters of cetyltrimethyl ammonium bromide (CTAB) in 0.001, 0.01, 0.05 and 0.1 mol·dm−3 aqueous solution of glycine in the temperature range 25–40 °C (at an interval of 5 °C) have been determined from density, speed of sound and conductometric measurements, respectively. The above calculated parameters were found to be sensitive to the interactions prevailing in the glycine–CTAB–water system. The analysis of the data was found to suggest that the ϕv and ϕκ values decrease sharply in the pre-micellar region and thereafter the decrease is almost linear at all concentrations of glycine, showing the dominance of hydrophobic interactions and facilitating the process of micellization. The ϕv and ϕκ values of these surfactants are found to be completely consistent with temperature over the entire concentration range. From conductance studies, the value of critical micelle concentration has been calculated, which shows dependence on the concentration of glycine as well as on temperature. A reasonably good qualitative correlation is found to exist with regard to CTAB–glycine interactions obtained from the conductance measurements and those from density and sound velocity measurements. All these observations demonstrate that this amino acid–surfactant system behaves in a different manner as compared to amino acid–electrolyte systems.