of the pure wood extract, mineral acids gave no 

 precipitate on titrating to the phenolphthalein end- 

 point. Further additions precipitated rosin and 

 humus together, the small quantity of humus 

 being entrapped by the gummy rosin. Direct 

 melting of the precipitate gave bright rosin, with 

 humus particles disseminated throughout. Extrac- 

 tion with ether involved some difficulty in separat- 

 ing the ether layer from the gelatinous humus, 

 but yielded a clean rosin of pale brown color. 

 On saturating the alkali extract with COz, partial 

 precipitation of both rosin and humus took place. 



The "Salting-Out" Method for Isolation 

 of Rosin 



Isolation of the rosin content of the alkali 

 extract was most conveniently accomplished by 

 salting out the rosin soap with caustic soda. 

 Sodium chloride was apparently just as effective, 

 but rather complicated the process by the intro- 

 duction of another reagent. The caustic soda meth- 

 od was chosen because direct and simple. Humus 

 itself is soluble in alkaline solution, but a small part 

 is carried down by the colloidal soap. Sodium 

 resinate is quite soluble in hot alkaline solutions, 

 as well as in neutral or faintly alkaline solutions 

 in the cold, but is only slightly soluble in cold 

 alkaline solutions when the concentration of free 

 caustic soda exceeds about 4 per cent. This solu- 

 bility determines the loss in recovery of the soap. 

 The method has the advantage of utilizing the same 

 reagent as is employed for extracting the wood and 

 cooking for pulp. No acid is necessary for precipitating 

 the free rosin, if the soap is to be used as such, and 

 no acid-resisting apparatus need be provided. The 

 alkali used in extracting the wood and precipitat- 

 ing the soap can be saved partly in the form of 

 sodium resinate (thereby enhancing the value of the 

 rosin fraction), and partly in the form of brown, 

 supernatant liquor to be used as a source of alkali 

 for the soda cook of the extracted chips. After 

 the pulping operation, the alkali can be recovered 

 in the usual way by evaporating, incinerating and 

 causticizing the waste soda liquor. 



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