Calorimetric Study on the Self Association of Promethazine Hydrochloride in Aqueous Solutions of High Ionic Strength

Abstract

The self association of promethazine hydrochloride in the presence of a high concentration of sodium chloride (0.6 mol dm−3) has been examined by the technique of heat conduction calorimetry. A theoretical treatment of the thermogenesis in solutions of amphiphilic compounds in which there is growth of the primary micelle at the critical micelle concentration by the stepwise addition of monomers is presented. This treatment gave a satisfactory representation of the calorimetric data and yielded values of stepwise association constants in good agreement with those derived from analysis of light scattering data using the same association model. Values are presented for the molar enthalpy changes for the stepwise addition of monomers and for the formation of the primary micelle.