Studies on Mixed Micellizations of Sodium Dodecanoate and Sodium Octanoate by Means of Electric Conductivity and Light Scattering

The critical micelle concentration (CMC), the counter ion binding constant (B) and the aggregation number (N*) for the mixed micellization of sodium dodecanoate and sodium n-octanoate as two anionic surfactants have been investigated by means of electric conductivity and light scattering. As its experimental results are found to be deviated from ideal mixed model, thus two different kinds of regular solution models such as Rubingh and Motomura are used for interpreting our experimental data. The stability of the mixed micelles has been confirmed from the negative values of the standard Gibbs energy of mixed micellization Delta G(micel,0) over all compositions and the measured values of Delta G(micel,0) agreed with the theoretical ones within the experimental error.