Perturbation of a nonionic microemulsion by the introduction of charged surfactant: II. Potentiometric titrations

Abstract A nonionic microemulsion which was perturbed by the addition of a small fraction of ionic surfactant, oleic acid, was studied by means of potentiometric titrations. The data were analyzed by a simple Debye-Hu¨ckle model for the electrolyte. The titrations gave a value of 6.6 for the intrinsicp K which implies that at the start of the titrations the car☐yl was in a region of low dielectric strength. Plots of the effectivep K vs the degree of ionization as a function of added electrolyte were analyzed to give an apparent radius of about 69A˚compared to the 50A˚found by classical light scattering.