AbstractFrom the same standpoint as Kagawa and Katsuura's opinion on the hydrolysis of cellulose sulfate, the authors argue that the spontaneous decomposition of cellulose xanthate in the course of ripening is ripening is wholly due to the alkali saponification which arises at the unionized ester‐group: magnified image magnified image Taking the characteristic features of the electrolytic dissociation of polymeric electrolytes into consideration, the authors derive theoretically the fomula of saponification velocity: The experimental results agree satisfactorily with this formula when n = 2. The authors also examine experimentally the variation in composition of viscose with especial reference to Na2S and Na2CS3 as the salt components, and explained the secondary reactions in ripening presumably as being caused by the successive decomposition of the primary decomposition product of xanthate, viz., dithiocarbonate, by the following mechanism, in which much stress is laid upon the ionization of reaction components: magnified image magnified image magnified image