The influence of porosity upon the distribution of reserpine in calcium sulphate granules

Abstract

Abstract Batches of calcium sulphate granules, all of the same size fraction but of widely differing porosities, were prepared from primary granules of different sizes. Each batch was coated with reserpine by spraying a solution of the drug in methylene chloride onto the granules whilst they were tumbled in a coating pan. The relation between the macroporous nature of the granules and their reserpine content was investigated. Low-pressure mercury porosimetry was used to obtain a quantitative estimate of the porosity and macropore size distribution of the granules, and their surface areas were determined by an air permeability method. Linear relations were obtained when the reserpine content was plotted against either the volume of mercury penetrating per gram of granules at 106·5 kN m−2 or their surface area.