ELECTRIC-CONDUCTIVITY ANALYSIS OF MICELLAR SOLUTION OF SODIUM DODECYL-SULFATE

Electric conductivities at 298.2 K of sodium dodecyl sulfate solution above the cmc were analyzed from the concentrations of counterion, surfactant ion, and micelle based upon the mass action model of monodisperse micelle formation, where the three micellization parameters (log K(n) = 230, n = 64, and m = 46.7) were employed. The ionic conductivity of micelle was found to be inconsistent not only with the micellar size of the identical charge but also with the conductivity of the dynamic radius of micelle of the identical charge. The inconsistencies could be solved by the hopping reaction of counterions between micelles through the overlapping of ionic diffuse double layers around micelle that takes place when two micelles come close together. The hopping reaction was found to start when the distance between micelles becomes less than 5 times the Debye length.