AbstractThe initial rate of hydrolysis of Egyptian medicated cotton with HCl or HCL‐FeCl3 as reagent, as well as the total carbonyl content of the hydrolysis products, were determined. The results obtained showed that although cellulose fibers are hydrolyzed more rapidly in an acid‐FeCl3 medium than in acid alone, the fibers resisted oxidation in a Fe3+ solution. Therefore the observed rate increase in Fe3+ solution cannot be explained on the basis of increased oxidation of hydroxyl groups. Consequently it has been suggested that the increase in the rate of hydrolysis is due to complexing between Fe3+ and the carbonium/oxonium ion or the leaving group. A comparison between the fine structure of the hydrolysis products of cotton cellulose by the use of HCl and HCl‐FeCl3 reagent is also given.