Conductometric and Viscometric Investigation of Cetylpyridinium Chloride in Water and in Aqueous Potassium Chloride

Conductance and viscosity measurements on cetylpyridinium chloride (CPC) in water and in presence of KCl were carried out as functions of concentration and temperature. From the conductivity data the critical micelle concentration (CMC) and degree of dissociation, a, of chloride counterions at various temperatures were obtained which were used to calculate the thermodynamic functions of micellization. The counterion dissociation was found to increase with temperature resulting in much greater contribution of enthalpy to micelle formation than is generally accepted. The binding of counterions to micelles increased with increase in concentration of counterions on addition of KCl and its temperature dependence also became less resulting in a decrease in the enthalpy contribution and corresponding increase in entropy of micellization. Intrinsic viscosity, [η_m], of the micellar surfactant solution obtained from the viscosity data were used to calculate the hydration of micelles. [η_m] was found to decrease both with increase of temperature and addition of electrolyte. The degree of hydration showed a similar trend.