ETHYL ALCOHOL, FROM WOOD WASTE. 51 



acidity based on the dry wood increased particularly the amount of 

 formic acid produced, whereas increasing the time of cooking seemed 

 to increase both acids, although the increase of formic acid was pro- 

 portionately much greater than that of acetic acid. 



The source of these acids at the temperatures used is apparently a 

 hydrolysis of the acetyl and formyl groups present in the lignin com- 

 plex, as suggested by Cross and Bevan 41 and by Cross, 42 who deter- 

 mined these acids as results of the acid hydrolysis of a number of 

 materials. Bergstrom 4: also obtained these acids as a result of hy- 

 drolysis without the aid of an acid catalyst, with the use of water at 

 6 atmospheres of pressure. Formic acid, however, with lsevulinic 

 acid, carbon dioxide, etc., is a decomposition product of the sugars, 

 and undoubtedly the large increases in formic acid yields with in- 

 creased pressure, time of cooking, and concentration of catalyst are 

 due to sugar decomposition. The data are of particular interest as 

 furnishing an approximate index of the degree of this decomposition. 



These acids in certain concentrations also have a toxic effect on 

 yeast growth and no doubt inhibit fermentation to some extent, even 

 in the neutralized juice in which the acids are present as their calcium 

 salts. In addition, nearly the same amount of acid was obtained at the 

 Forest Products Laboratory as is usually obtained by the destructive 

 distillation of this species of wood, and in a few cases more. It is known 

 that the rapid decomposition of wood does not begin till a tempera- 

 ture of 275° to 280° C. 44 is reached, after which the decomposition is 

 exothermic. Since the formic acid is derived from the wood and also 

 from sugar decomposition, the amount hydrolyzed from the wood 

 directly is. difficult to determine. If this amount were known, it 

 would give a helpful index, similar to the methoxy number now used, 

 of the value of a species of wood for certain purposes. It has been 

 shown beyond question 45 that the destructive distillation of cellulose, 

 sulphite, or soda wood pulp, as well as cotton, yields acetic acid, but 

 no methyl alcohol, and Klason and his coworkers have obtained a 

 yield of 2.79 per cent of acetic acid from spruce sulphite cellulose. 

 More than this amount of acetic acid was obtained in cook No. 56 at 

 the Forest Products Laboratory by hydrolysis of the wood at a tem- 

 perature 100° C. lower. 



In view of the work of Cross and Bergstrom, it seems that the greater 

 part of the acetic and formic acids, with the exception of the formic 

 acid that results from sugar decomposition, comes from the hydrolysis 



41 Cross and Bevan, Berichte, 28, 1940. 



42 Cross, W. E., Dissertation, Gottingen, 1910, Ueber das Vorkommen der Formyl- und Acetyl Gruppen 

 im Lignin. 



43 Bergstrom, Der Papierfabrikant, 2, 305. ' 



44 Klason, P., Jour, fur prakt. Chemie, 1914, 90, 413-447. 



45 Buttner, G.,and Wislicenus, H., Jour, fur prakt. Chemie, 79, 177-234; Klason, von Heidenstam, and 

 Norlin, Zeit. fur ang. Chemie, 1909, 1205. 



