PRODUCING SODA PULP FROM ASPEN. 5 



While the manufacturer of paper pulp is interested in these chemical 

 investigations they do not give him much practical information on the 

 interrelation of the various cooking conditions which he employs and 

 the effect of their modifications on the yield and quality of the pulp. 



An article published by Tauss 1 in 1889, dealing with the effects of 

 water alone on cellulose-containing materials, is of interest in connec- 

 tion with the Forest Service tests because the "yield" or residue with 

 zero caustic soda assists in determining the curve for the effect of 

 amount of caustic soda on the yield of crude pulp (fig. 4). Tauss's 

 experiments showed (Table 1) that a very appreciable amount of 

 solids can be extracted from wood and from cellulose by boiling in 

 water, especially at high pressures. In 1890 the same author 2 pub- 

 lished the results of investigations in which caustic-soda solutions were 

 employed in the place of water alone. The experiments with caustic 

 soda were made partly with solutions of a concentration employed in 

 commercial practice, partly with more concentrated, and partly with 

 more dilute solutions. 3 The calculated residues (Table 1) afford some 

 interesting comparisons with the Forest Service yield data. 



In 1907 De Cew 4 published a technical article dealing with the func- 

 tion of the soda process in the production of wood cellulose. Although 

 no data are cited to substantiate his conclusions, he makes the fol- 

 lowing statements : 



The results obtained with, this process depend very largely upon the accuracy with 

 which it is carried out. The action of caustic soda is one of hydrolysis, in which the 

 woody molecule is gradually broken down with the formation of acid products which 

 combine with and neutralize the alkali, leaving the cellulose in the form of isolated 

 fibers. Now, if sufficient alkali were used and the cooking action continued, the entire 

 fiber would finally be dissolved, although the more resistant celluloses would be the 

 last to disappear. It is, therefore, necessary in order to bring into solution only the 

 lignified portion of the wood to add just sufficient alkali for this purpose. 



This is almost entirely neutralized by the acid products formed from the lignocellu- 

 lose, and thus very little free alkali is left in the liquor to attack the rest of the fiber, 

 which should be almost pure cellulose. At first the alkali is very active and a rapid 

 combination takes place, but the rate of reaction becomes continually slower as the 

 free alkali grows less and the resistance increases. There are also such varying con- 

 ditions as to causticity, pressure, circulation, and time of cooking, which are of con- 

 siderable importance in the process, for some makers are obtaining from 1-200 pounds 

 of fiber per cord more than others in treating the same kind of wood. 



i Dingl. Polyt. J., pp. 27&-285, vol. 273, 1889; Jour. Soc. Chem. Ind., p. 913, vol. 8, 1889. 



2 Ibid., pp. 411-428, vol. 276, 1890; Jr. Soc. Chem. Ind., p. 883, vol. 9, 1890. 



s See footnote, p. 16. 



* Jour. Soc. Chem. Ind., pp. 561-363, vol. 26, 1907; Chemical Abstracts, p. 319, 1908. 



