Partial Surface Excess and Intermolecular Interaction Studies on Mixed Surfactant Systems

Surface tension measurements have been carried out using lecithin and dodecyl pyridinium chloride separately and in combination, with a view to examine the variation of CMC with composition and to have an estimate of the intermolecular interactions amongst the surfactant molecules. Estimation of the surface excess when the surtactant mixtures of different compositions are used, has also been carried out. The surfactant mixtures exhibit non-ideality in a substantial measure as evidenced by the so-called 'excess surface excess' and the nature of its variation with composition. An attempt has also been made to obtain a quantitative estimate of the interactions on the basis of the regular solution theory.