In order to investigate the effects of hydrolysis at the latter stage of bisulfite cooking upon the fine structure of wood cellulose, the experiment stated as below was carried out. The holocellulose, which has been prepared from red pine in the same manner as previously reported in part IX, was hydrolyzed under following conditions, namely: temperature 100, 135 and 170°C, pH 7.0, 3.0, 1.5 and 1.0; retention time at elevated temperature 3 hrs. With each hydrolyzed holocellulose, its yield from original holocellulose, the amount of crystalline region in it, the rate of degradation of crystalline region, leveling-off DP etc. were determined. The results were as follows:
1. With the progression of acid hydrolysis, the holocellulose has gradually dissolved and decreased in its average DP and also in its leveling-off DP, while the content of crystalline region in it increased. These results were quite similar to that as previously reported in Parts I and IX.
2. With the hydrolyzed holocellulose, which has been degraded to the same average DP under different conditions, the higher the temperature the less its leveling-off DP and also its Kc. (degradation constant of crystalline region)
3. The hydrolyzed holocellulose with same average DP, has about the same amount of crystalline region in it, irrespectively of the temperature and pH during acid hydrolysis. However its yield from original holocellulose decreases under the higher temperature.
From these results it could be presumed that the acid-hydrolytic reaction at the latter stage of commercial sulfite cooking has a fairly strong influence even upon the fine structure of wood cellulose according to the pH and temperature in its acid medium.