On the Chlorine Numbers and Lignin Content of High-yield Pulp

Abstract

In the determination of lignin content and chlorine number of high-yield pulps, the reproducibility of results and correlation between those each two values were studied.
Pulps used were made from two soft woods and two hard woods by neutral sulphite semichemical process, and ranged in lignin content from 5 to 24 %.
Lignin was determined according to TAPPI Standard T 222 m-54, and chlorine number was determined by four methods, e. g. Roe's (TAPPI Standard T 202m-45), the modified Tillage's Ueno's and the improved method, deviced by authors combining above two.
Results obtained were summarized as follows :
1. The correlation between lignin content and Ueno's method was good linear relationship through out all woods.
2. In the case of the modified Tingle method and the improved method, the correlation between lignin content and those one differed from species, namely soft wood and hard wood.
3. Those linear functions, showing the correlation, were consisted of two parts having a refraction point at 14 % lignin content.
4. The coefficient of lignin content to chlorine number increased with lignin content, but differed from methods, excluding Ueno's one, and species.
5. It was found that the correlations among chlorine numbers were better than the correlation between lignin content and chlorine number.
6. The correlations that authors have found between lignin content and each chlorine number, were differ from relations which had been reported by many researchers.
These were probably due to differences in lignin content, pulping method, wood species used and other unknown factors.
7. From the stand point of the reproducibility of results, it could not experimentally evaluate that which method was best one.
8. In preparing of the dried pulp samples, light at determination and drying temperature. room one to 105°C., have not been found to exert a marked influence on the determination of the Roe chlorine number.