The dissolution of salicylic acid in micellar solutions of polysorbate 20

Abstract Dissolution rates of salicylic acid in micellar solutions of polysorbate 20 have been determined at pH 1·0 to 4·0 using a pH-stat to maintain the pH. At any one pH, as the concentration of polysorbate 20 was increased up to 12% w/v, the dissolution rate increased, but a further increase up to 20% w/v polysorbate 20 only slightly increased the dissolution rate. At any one concentration of polysorbate 20 the dissolution rate increased linearly as the pH was increased. The dependence of dissolution rate on such parameters as viscosity of the dissolution medium, diffusion layer thickness and diffusion cofficient has been examined.