APPLICATION OF pH MEASUREMENT TO DETERMINE THE MICELLAR PROPERTIES OF MIXED BILE SALT AND NONIONIC SURFACTANT SYSTEMS

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Abstract
This paper applies pH measurement to determine the micellar dissociation concentration (mdc) and the critical micellar concentration (cmc) of mixed sodium cholate (or sodium deoxy-cholate) and octaethylene glycol mono n-decylether nonionic surfactant systems. The experiments were performed by diluting the mixed surfactant solutions with freshly distilled water and following the pH changes with a hydrogen ion electrode at 25°C. Two breaks appear in the pH-concentration plots of the mixed surfactant systems, signifying mdc and cmc. The cmc values for the mixed micelles are in good agreement with values reported in the literature. One may also estimate the cmc of the pure component from data obtained for the mixture without going through the trouble of sample purification. The method of using pH measurement to determine mdc and cmc is quick and simple. It requires little training.