Electrochemical study of the thermodynamics of micellization of hexadecylpyridinium bromide

A membrane electrode selective for hexadecylpyridinum bromide was used to study the micellization of the surfactant at various temperatures (25-50 degrees C). The thermodynamic parameters Delta H degrees(m) and Delta S degrees(m) were calculated from the temperature dependence of the equilibrium constants for micellization of the surfactant. It was clearly shown that the entropy of micellization Obtained by the usual approximate method from Delta G degrees(m) = (2 - alpha)RT1nX(cmc) is much more positive than the corresponding exact value calculated from direct activity measurements.