| Abstract: | SUMMARY. In a series of kraft pulps cooked to different yield levels, the content of phenolic hydroxyl groups pre¬sent in the residual lignin has been quantitatively deter¬mined by means of aminolysis. For comparison, a soda pulp and the corresponding wood material were also ana¬lysed. The results obtained demonstrate that during the course of a kraft cook there is an increase in the content of phenolic hydroxyl groups per unit weight of residual lignin. Throughout the cook the content of these groups is, how¬ever, much lower than the content of phenolic hydroxyl groups present in the dissolved kraft lignins. It was further found that the residual lignin in a soda pulp contains a significantly smaller amount of phenolic hydroxyl groups than the lignin in a kraft pulp at the same degree of delignification. The importance of these results is discussed with refer¬ence to known features of alkaline pulping processes. |
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