On the State of Pentosan in Wood Pulps

Abstract

Abstract 1. The pulps from the red pine and beech were hydrolyzed with boiling 4n hydrochloric acid solution for 1–7 hours and a part of the hydrolyzed pulps was treated with boiling 1% sodium hydroxide solution for half an hour to eliminate recrystallized particles. The pentosan content decreased as a function of the pulp yield. The degrees of polymerization of these samples were determined. 2. The pulps from the red pine and beech were treated with 4-17.5% sodium hydroxide solution for half an hour at 20° and this procedure was repeated. A part of the samples treated with the alkali was hydrolyzed with 2.5n sulfuric acid solution for one hour at 95–100°. The pentosan contents of these samples were determined. 3. The results show that it is difficult to reduce the pentosan content of wood pulp to under 0.5% by intermicellar reactions such as acid-hydrolysis or dilute hot alkaline refinement, whereas by intramicellar reactions such as cold concentrated alkaline refinement, it is easy to reduce the pentosan content to under 0.5%. The resistant pentosan seemed to be built in the crystalline region of wood cellulose. 4. It has no good effect for pentosan removal to eliminate the recrystallized particles produced by acid hydrolysis with dilute alkali, while acid treatment after cold alkaline refinement gave good result for pentosan removal.