In order to inhibit recrystallization during acid hydrolysis, a commercial viscose grade pine sulfite pulp was preoxidized with 0. 1 N NaOH-0. 1 N NaOBr solution for various hours at 25 °C, washed, dried, and then subjected to hydrolysis with 3. 5 N aq. HC1 at 100 °C, Amount of highly ordered regions (crystallinity estimated by acid hydrolysis method), degree of polymerization and moisture regain of resulting hydrocellulose were determined to compare the inhibiting effects. Preoxidation should

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... e carried out for the hours corresponding to the inflexion point of the time of oxidation vs. oxygene consumption curve. The preoxidation for less hours gives an imperfect inhibiting effect, and that for more hours causes oxidative degradation of the highly ordered regions. The preoxidation method is more effective than the preethanolysis method described in the previous paper. Preoxidation after preethanolysis which increases accessibility of fiber to the oxidizing reagent gives only a slightly higher effect, showing that recrystallization is inhibited perfectly by the preoxidation method. However, hydrocellulose obtained by this method contains more carboxyl and carbonyl groups than ordinary one, though the absolute amounts are low. Therefore, the preethanolysis method without successive preoxidation is recommended when hydrocellulose is prepared as a sample for further investigation.