INFLUENCE OF MICELLES ON TITRATIONS OF AQUEOUS SODIUM AND POTASSIUM SOAP SOLUTIONS

Sodium and potassium caprate, laurate, and myristate solutions below and above the critical micelle concentration were titrated with HCl. The cationic activity (H+, Na+, K+) was monitored during the titrations using a pH glass electrode and a cationic glass electrode. The curves of pH vs. HCl added can be theoretically calculated for these systems from equilibrium considerations. The simultaneous monitoring of H+ and K+ activity during the course of a titration of a micellar laurate solution leads to the conclusion that H+ ions compete with K+ ions at the negatively charged micelle-solution interface. The effect of charged interfaces on the ionic distribution is discussed in terms of the apparent surface concentrations of counterions.