SynopsisWood pulps highly reactive in both high-and low-catalyst cellulose acetate processes can be prepared by mercerization and then treatment with alkylene oxides; only trace levels of substitution are required. The fiber inactivating effects of mercerization after drying are overcome, and several acetate properties are improved by this process. The reactivity characteristics cannot he duplicated by similar modifications of nonmercerized fibers; in low catalyst processes such pulps actually show reduced reactivity.