Cmc of mixtures of chlorpromazine hydrochloride and polysorbate 80 determined by pH measurements.

The cmc of mixtures of chlorpromazine hydrochloride and polysorbate 80 was determined by pH titration. The values thus obtained coincided with those determined by the surface tension method. The mixtures studied could be divided into two groups according to the shape of their pH concentration curves. For mixtures containing less than 0.8 mole fraction chlorpromazine, the curves suggest that some interaction occurs in the premicellar concentration range. For mixtures containing more than 0.8 mole fraction chlorpromazine, the curves suggest that the micellar process occurs in more than one step.