Abstract
The interaction between methyl red (azo dye) and cetylpyridinium chloride (cationic surfactant) in the methanol-water system were studied using a spectrophotometric technique. Variable parameters like constant dye concentration and its structure, surfactant concentration, pH, absorbance, and solvent composition were studied. Using the UV-Vis technique, critical micelle concentrations (CMCs) of cetylpyridinium chloride were measured with methyl red. The spectral data were analyzed and determined the differential absorbance, binding and partition constants, partition coefficient, the Gibbs free energy of binding and partition in mixed solvent media (0.1, 0.2, 0.3, 0.4 volume fraction (v.f.)s of methanol, respectively).