AbstractThe kinetics of the degradation of cellulose triacetate in chloroform/acetic anhydride mixtures containing a perchloric or sulphuric acid catalyst was studied. The change in molecular weight with time was followed viscometrically, employing Maron's singlepoint method to evaluate limiting viscosity number values and using appropriate Mark‐Houwink constants for the chloroform/acetic anhydride mixtures. The dependence of the first‐order rate constant on concentration of catalyst, acetic anhydride, and cellulose triacetate, as well as polymer molecular weight and temperature was investigated. An explanation of the results, based on both H+and Ac+(acetylium ion) acting as the catalytic degradation species, is given; this is also shown to account for the degradation behaviour in similar cellulose acetate systems observed by previous work