Permitivity of penicillin V: a thermodynamic study

A method of determining critical concentrations for aggregation in self-associating systems of low aggregation number by dielectric constant measurement has been applied in a study of the self-association of penicillin V as a function of temperature. Dielectric properties of penicillin V are more sensitive to structural modifications in bulk amphiphilic solutions than the electrical conductivity and provide a simpler method for the determination of critical concentrations of such systems without the necessity of the complex numerical data analysis required in the determination of inflection points in electrical conductivity data, which show a more gradual change throughout the measured concentration. Thermodynamic parameters of micelle formation were derived from the variation of the first critical concentration using a modified form of the mass action model applicable to systems of low aggregation number. The good agreement between the experimental and theoretical standard enthalpies of aggregation,ΔH°m, supports the validity of the proposed model to predict thermodynamic parameters of aggregation.