The study of synergism between N-lauryl sarcosine sodium and lithium dodecyl sulfate using conductometric technique

Surfactants tend to associate as micelles; self-aggregation of surfactants in an aqueous medium is a subject of much interest in the field of surface chemistry. Synergism in the formation of mixed micelle survives as the cmc of mixed system is lower than that of each amphiphiles. In this work we have investigated the mixed of two anionic surfactants at different mole fraction. Two anionic surfactant with commercial names N-lauryl sarcosine sodium(NDS) salt and lithium dodecyl sulfate (LDS) used in this work. Specific conductivities (k) of the solutions (either pure or different mole fractions) were measured using a Consort conductometer (model C860) at 30.0 °C.In this study reports the interaction between two anionic surfactants (NDS and LDS) in the water at different mole fractions by conductometric method. The critical micelle concentration (CMC) calculated in pure and mixture state. Also, the micellar mole fractions of surfactants ( 1 id X and 1 m X ), interaction parameters ( m ), degree of counterion binding (α) and standard Gibbs free energies of micellization( 0 mic G ) values were evaluated and discussed[1-2]. Fig. 1 shows plots of specific conductivity, k, vs concentration of surfactant in pure of LDS and mixture; above a certain concentration, the slope changes; this concentration is taken as the cmc.For all mixtures of NDS/LDS, the results indicate an attractive interaction (negative m  -values), which confirming synergistic interactions between two surfactant. Also, activity coefficients ( 1 m f and 2 m f ) are always less than unity suggesting non-ideality in the mixtures.