Critical micelle concentrations (cmc) of dodecyldimethylamine maximum in the range a M ร 0.5 (23). In the hydrogen ion oxide (DDAO) were determined at 25ะC in solutions in the absence titrations the intrinsic dissociation constant of the micelle of salt at different pH values by four methods: surface tension, has been known to be smaller than that of the monomer (5, dye solubilization (Sudan III), pH-concentration break points, 7). These characteristic properties have been interpreted in and counterion (Cl 0 ) activity. With the aid of the cmc values, the terms of the hydrogen bond formation between the nonionic degree of ionization of DDAO micelle a M was determined as a and the cationic pair (24). Our recent study on the effects function of pH from the hydrogen ion titration. The cmc increased of ionic strength on the cmc of DDAO has revealed the sharply in a narrow range of a M from 0.35 to 0.40. This destabilizainteresting result that the cmc of the cationic species is lower tion of micelles was also noted on the anomalous change of pK on the hydrogen ion titration curve. The counterion activity was at high ionic strengths (higher than 0.2 M NaCl) than that measured potentiometrically, and the degree of the counterion of the nonionic one (25). A hydrogen bond for the cationicbinding u was determined as a function of a M . The value of u cationic pair is thus suggested (24). We expect the assumed showed a sharp increase with a M also around 0.4. The line width hydrogen bond between the cationic head groups will be of NMR absorption peak of 35 Cl ions was well correlated with a M . considerably weakened or destroyed in the absence of salt The surface electric potentials c 0 of DDAO micelles were evaludue to strong electric repulsion. A Monte Carlo calculation ated from both the hydrogen ion titration and the acid-base indihas suggested that the cationic-cationic hydrogen bond cators, and the former value was larger than the latter one. A should be nearly as stable as the cationic-nonionic one in procedure is proposed to compare the stabilities of the micelles order to explain the experimentally observed a M dependence having different a M values. The result indicates much larger deof the cmc (26). In the present study, the stability of the pendences on a M than those uncorrected for different ionic micelles (cmc), counterion activity, hydrogen ion titration, strengths at the cmc.