Increased Consumption of Pulping Liquors

Conifers and some hardwoods containing significant amounts of resinous components are best pulped by the kraft process. The free resin acids and fatty acids are neutralized by the alkali, their esters are saponified, and the alkali is lost in the tail-oil recovery system. 

The hot-water solubles content or the hot dilute alkali (0.1 N NaOH) solubles content have been used as indexes of the amount of alkali-consuming polyphenols present. The values are only comparative, as the materials removed contain not only polyphenols but also organic acids and the simple carbohydrates. Nevertheless, useful information is obtained. In a study to determine the cooking conditions that would yield pulps of specified lignin content from pale-colored euca-lypts, a relationship was found between hot-water solubles and the amount of alkali consumed (31)  

Furthermore, it was found that the relationship between hot-water solubles and alkali requirements for a specified lignin content in the pulp was less accurate. From this behavior there were indications of a rapid retardation of delignification 

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