Dissolution Rates in Surfactant Solutions Under Stirred and Static Conditions

Abstract

The dissolution rate of benzoic acid was determined in water and solutions of polyoxyethylene (23) lauryl ether by the rotating disk and static disk methods. The results under stirred and static conditions substantially deviated from the Noyes-Whitney equation. Dissolution rates in surfactant solutions were much less than anticipated on the basis of solubilization data. The ratios of dissolution rate in surfactant solution to that in pure solvent were found to be significantly greater under static conditions as compared to the ratios determined under stirred conditions, suggesting a possible change in dissolution mechanism. Certain aspects of dissolution rate theory are explored to explain this unusual phenomenon. The dissolution rate of benzoic acid was determined in water and solutions of polyoxyethylene (23) lauryl ether by the rotating disk and static disk methods. The results under stirred and static conditions substantially deviated from the Noyes-Whitney equation. Dissolution rates in surfactant solutions were much less than anticipated on the basis of solubilization data. The ratios of dissolution rate in surfactant solution to that in pure solvent were found to be significantly greater under static conditions as compared to the ratios determined under stirred conditions, suggesting a possible change in dissolution mechanism. Certain aspects of dissolution rate theory are explored to explain this unusual phenomenon.