On the interpretation of the conductivity of soap solutions

It is shown that measurement of the conductivity of micellar solutions provides a rather sensitive test regarding the size distribution of the micelles. In a number of systems the micelles are found to be practically uniform. In this case information on the equivalent conductance of the micellar soap can be obtained from the conductivity data in the range above the cmc. The data in the transition range (around the cmc) can be interpreted with the help of the law of massaction and lead to the molecular weight of the micelles. Anomalous conductivity curves with a maximum slope just above the cmc are interpreted in terms of a wide size distribution of the micelles.