Thin films were prepared by the method of evaporation of aqueous solutions of chitosan or its mixtures with poloxamer 407, gelatin, or polyvinyl alcohol. Films of varying thickness were cross-linked with phosphate ions. They contained micronized folic acid in a concentration of 9.1 % or 3.2 %. Prolonged several hours’ liberation of folic acid into isotonic phosphate buffer at pH 5.5, 6.0,and 6.5was examined. In the initial stage, the mechanism of liberationwas governed by diffusion of the dissolved fraction, at higher pH values a higher rate of dissolution of the substance played its role. In some composites, sorption of folic acid to chitosan in an extent dependent on the composition of composites and current acidity of the medium was demonstrated.

        Key words: chitosan – composites – thin films – folic acid – liberation