A diffusion cell to model the permeation of salicylate drugs through the skin using low-cost materials and a sensitive colorimetric analytical technique is described. The diffusion apparatus has been used at a further education college by a student for her AS-level Extended Project to investigate the permeation rates of salicylic acid (2-hydroxybenzoic acid), its methyl ester and its sodium salt. The diffusion cell could be used for further investigations including studying other salicylic acid derivatives and/or various salicylic acid topical formulations. (Contains 8 figures and 2 tables.)