In reality the degree of protonation depends upon the surroundings of the surfactant, i. e. the effect of self-aggregation on the acid-base equilibrium of one of these surfactants is a known effect resulting in a 'pK m ' (apparent pK a for micellar surfactant) shifted from the aqueous counterpart by factors such as hydrogen bond availability, dielectric constant changes, surfactant distribution in the micelles, and overall surfactant concentration. Vu et al. determined the effect of the cosurfactant cocoamidopropyl hydroxysultaine (CAHS) on SLSar by potentiometric titration, observing a shift from pK a ≈ 5 to 4.5 when going from pure SLSar to a CAHS/SLSar mole ratio of 60:40.