August, 1925
I S D C S T R I A L A S D ESGISEERISG CHESIISTRY
change in acid concentration is not possible in present commercial practice. It is a quite fortuitous circumstance that the resistance of the desired fibrous carbohydrate material of wood to sulfurous acid hydrolysis should be such as to permit the removal of the lignin by the same reagent, and it is further remarkable that such a wide variation in cooking conditions should produce approximately the same amount of pulp of approximately the same composition. The picture of the course of the sulfite pulping reactions that can be drawn from the foregoing results is not that of a successive breaking down of the wood in various parts, but rather that of a set of simultaneous reactions proceeding a t different rates.I5 Effect of Acids and Salts on Cooking Action
With reference to the changes that might be manifest in the qualities of the residual fibrous material as a result of adding reagents to alter the rate of lignin removal, much speculation has prevailed, and some experiments are on record. The following cooks, the results of which are given in Table IV, were performed to show the effects producible by the addition of a few simple chemicals to the cooking liquor. As standards of comparison, Cooks 67 and 68 were made with 1.05 per cent and 0.55 per cent excess sulfur dioxide, respectively. A 6 hours’ cooking period was allowed in all cases, and conditions were identical in all respects except for the addition or substitution of some reagent. In Cooks 63, 64, and 65 enough hydrochloric acid, sodium chloride, and acetic acid, respectively, were added to produce 0.5 per cent concentration of each in a cooking acid containing the usual 1 per cent combined sulfur dioxide and 0.5 per cent excess sulfur dioxide. The results in all three cases show a tendency toward the removal of more lignin and cellulose than in Cook 68. The difference is most decided where hydrochloric acid was added. Cook 71, in which sodium bisulfate was added, also shows a tendency toward rapid removal of lignin and cellulose, while in Cook 82, with sodium acetate, the same cellulose destruction is seen with less lignin removal. Cook 70, with an extra 0.5 per cent of sodium bisulfite, is little different from the control in Cook 68. In Cooks 72 and 81 the only base present was that addedassodium chloride and sodium acetate in amounts equivalent to the quantity of sodium bisulfite necessary to give 1 per cent combined sulfur dioxide. I n Cook 72, containing sodium chloride, a decided increase in the destruction of cellulose is seen without accompanying acceleration in lignin removal; the pulp was decidedly burned. Cook 81, with sodium acetate, shows a decided and general slowing up of the reaction. It is unprofitable to generalize too widely on results with such small positive differences, but it may be observed that there is a tendency for strong acids and salts of strong acids to “speed up” the reaction, whereas weak acids or salts of the same have a contrary effect if any. Such a generalization points directly to the theory of the pulping process as an acid hydrolysis of wood, and to a consideration of the influence of the concentration of the hydrogen ion on the pulping process. Results of experiments to establish the possible relation of hydrogen-ion concentration to the sulfite pulping process will be included in a future paper of this series. Du Pont Rayon Company Extends Acreage of Tennessee Plant-The du Pont Rayon Company has purchased from the Nashville Industrial Corporation a tract of 245 acres at Old Hickory powder plant for $175,000. About two years ago the company purchased over 500 acres of land from the corporation and its $4,000,000 rayon plant is located on the site. The new purchase includes some of the large buildings erected during the World War, and the sale was made under wartime restrictions required by the Federal Government.
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Effect of Presteaming on the Hydrolysis of Wood’ By E. C. Sherrard and J. 0. Closs FOREST PRODUCTS LABORATORY. MADISON. WIS.
In order to complete a study of the variables affecting the yields of sugar and alcohol from wood by acid hydrolysis, wood was subjected to different periods of steaming both before and after the addition of acid. In these experiments the diluted acid was injected into the digester under pressure without interrupting the digestion. Fermentations and alcohol determinations were made on the sugars thus produced in order to determine the effect of such conditions upon the yield of fermentable sugars. The results obtained indicate that a presteaming causes little or no increase in yields of total sugar. Longer steaming at 8 kilograms or less after addition of the catalyst produces somewhat larger yields and at the same time produces a greater percentage of total sugar fermentable.
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N 1912 Cahoe2 described a series of investigations on t h e
hydrolysis of wood, in which the wood was presteamed prior to the introduction of the catalyst. Hydrochloric acid was used as a hydrolyzing agent and experiments weremade on both laboratory and commercial scales. Cahoe’s reason for resorting to presteaming was that not all of the sugars produced under ordinary conditions were fermentable. He reasoned that the presence of the hydrolyeing agent during the heating stage of the reaction might have a harmful effect on the final products. I n order to prevent such a result the wood was first treated with steam alone. After i t had been steamed sufficiently the pressure was removed, the acid introduced, and the pressure treatment resumed. From the experiment as performed under these conditions he concluded that the main hydrolytic reaction is practically instantaneous, a conclusion later confirmed by K r e ~ s m a n n . ~His further inference that the reaction runs to an equilibrium was not entirely borne out in a recent investigation by Sherrard and Gauger,* in which added sugars were not materially affected by the conditions imposed. Since Cahoe’s paper is rather incomplete in that very meager data are given regarding the conditions used, it was decided to conduct a similar series of experiments using sulfuric instead of hydrochloric acid. Preliminary experiments with a small autoclave5 had already indicated that steaming without a hydrolyzing agent produces about 5 per cent of total reducing material calculated on the dry weight of the wood. The residue remaining after the extraction of the reducing material, upon hydrolysis with sulfuric acid as a catalyst, p:oduces approximately 17 to 18 per cent of additional reducing sugar. The total sugars thus obtained amount to 22 to 23 per cent of the dry weight of the wood, a quantity that corresponds to the yields obtained under the standard conditions outlined by KressmanneG Inasmuch as Cahoe reports a yield of 25 to 29 per cent total reducing sugar, it was thought desirable to repeat his work with slight variations. Besides the substitution of sulfuric for hydrochloric acid, his process was varied to the extent that the original steaming pressure was not reduced but in1 Presented before the Division of Cellulose Chemistry at the 69th Meeting of the American Chemical Society, Baltimore, Md., April 6 t o 10, 1925. * J . Soc. Chem. Jnd., 1 , 513 (1912). a c‘.S . DepC. d g r . , Bull. 983, 12. 4 THISJOURNAL, 16, 63 (1923). Described in THIS J O U R N A L , 16, 611 (1923). 0 U.S. Defit. A g r . , Bull. 983.
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I N D LrSTIZI.4 L A N D ENGINEERING CHBJUSTRY
848
stead the acid was injected into the digester when the pressurti \!-as at a maximum. ils Kressmeiin had obtained the best yields with 2.5 per cent sulfuric acid and 125 per cent water, the same coriditions were selected as being the best suited for t,his work. The effect of both time and pressure during the presteamiug ueriod as well as after the addition of the acid w:is notcd. Apparatus T h e hydrolysis of the sawdiist wils caiiicd 011 iii a rotary di.
