At the TX-100 and CTAB mixture concentration in the solution at which its micelles can be present (Figs. 9 and S19), the changes of as a function of ethanol concentration are quite different from that at the mixture concentration lower than CMC. The conductivity changes in the range of low ethanol concentration almost in the same way as the apparent molar volume of ethanol. The decrease of conductivity is connected with the decrease of the CTAB dis-sociation both in the monomeric form and in the micelles. On the other hand, as the measurements of the micelle size indicate, the micelle size decreases as a function of ethanol concentration inthe range in which alcohol is present in the monomeric form insolution. It is possible that the micelle density changes also in this range of ethanol concentration. It is also probable that the degree of counterion binding to the surface active ion increases slightly ina certain range of ethanol concentration. Due to the effect of the semagnitudes on the conductivity, the minimum of (Figs. 9 and S19)is observed on the isotherms of conductivity in the range of ethanol concentration in which the presence of TX-100 and CTAB mixed micelles cannot be excluded. The changes of the degree of the counterion binding to the surface active cation and of the size of the micelles are confirmed by the changes of the conductivity as a function of the TX-100 and CTAB mixture concentration and only the CTAB concentration (Figs. 4 and 10). The values of CMC deter-mined from the conductivity changes as a function of surfactant mixture concentration at the constant ethanol concentration equalor higher than 1.07 M are considerably larger than those obtained from the surface tension, density and viscosity isotherms (Table 3).If the conductivity is plotted against the CTAB concentration(Fig. 10), then the influence of TX-100 in the mixture in the bulk phase on is evident over the surfactant mixture concentration higher than CMC. At the same CTAB concentration, the bigger mole fraction of TX-100 in the bulk phase, the bigger value of the specific