[Construction, operation and initial experience with a laboratory apparatus for fluid-bed coating of particles]

Starting from the developmental work of Dittgen and co-workers [1] and of Gröning [2], the authors constructed an air-suspension device which permits to coat crystals, granules and pellets on a laboratory scale. The device developed is a glass apparatus for coating almost 10 g of particles. The motion of the particles to be coated is characterized by a high-speed rotation on a circular orbit associated with a raise by the air current and a fall caused by gravity. This combined motion prevents the development of zones of varying particle sizes. The usefulness of this apparatus is demonstrated by the example of the application of a polyacrylate depot coating to pholedrine sulphate and quinidine sulphate pellets. Scanning electron micrographs are used for the optical assessment of the coating.