Abstract The surface tension and the conductivity methods were used to determine and compare critical micelle concentrations of anionic surfactant sodium dodecyl sulfate and nonionic p-octyl polyethylene glycol phenyl ether solutions. The surface tension of two surfactants solutions with different concentrations were measured by hanging ring method. The saturated adsorption capacity, critical micelle concentration and molecular cross section area were obtained. The conductivity curves of the above two solutions were studied by conductance method, and the critical micelle concentration of the sodium dodecyl sulfate were only obtained. Compared with the conductance method, the surface tension method can get more information about the properties of surfactants and is more widely used. The experiment enables students to gain a better understanding of the nature of surfactant critical micelle concentration and the methods of measurement, to identify the advantages and disadvantages of different methods, and to broaden their knowledge. This will lay a good foundation of further study and application of surfactants for students in the future.
ZHANG Xiao-Guang. Comparison of Determination of Surfactant Critical Micelle Concentration by Surface Tension and Conductivity Methods[J]. Chinese Journal of Chemical Education, 2021, 42(18): 134-136.