70 HATCH EXPERIMENT STATION. [Jan. 



The lignin acids are probably strongly united to the dex- 

 trose cellulose, and it seems reasonable to suppose also to 

 the pentoso cellulose. 



(b) Recognition of the Pentosans. 

 By treating wood with dilute alkali, and precipitating the 

 extracted material with alcohol and hydrochloric acid, Th. 

 Thomson^ obtained a substance termed wood gum (Holz- 

 gummi) ; and by inversion Koch^ secured wood sugar or 

 xylose, which was carefully examined by Wheeler,^ Allen* 

 and Tollens, and declared to be a pentose (C^ff^O''). The 

 mother substances in wood gum and also in cherrj^ gum^ 

 contain less water than the pentoses, and are termed pen- 

 tosans (C^H^O*) . The substance yielding xylose was termed 

 xylan, and that yielding arabinose, araban. 



(c) Methods for Determination of Pentosans. 



After wood gum and the resulting sugar had been care- 

 fully studied, it became necessary to obtain a method for 

 their quantitative determination, in order to note to wliat 

 extent they occurred, especially in agricultural products. 

 The first experiments were made by Stone, Wheeler, Allen 

 and Tollens,*^ by dissolving the substance in hydrochloric 

 acid, precipitating the furfural with ammonia, and weighing 

 the resulting furfuramid. 



Gunther^ and Tollens distilled with hydrochloric acid of 

 1.06 specific gravit}^, and titrated the distillate with acetate 

 of phenylhydrazine, using analine acetate as indicator. 



Stone ^ proposed a method in which he titrated the dis- 

 tilled furfural with a dilute solution of phenylhydrazine of 

 known streno;th. usino: Fehlinof solution as indicator. 



De Chalmot^ and Tollens precipitated the furfural distillate 



1 Journal for Pract. Chem., 19, (2) p. 146. 



- Pharm. Zeitsch. fiir Russland, 25, p. 619, 635, 651. 



^ Liebig's Ann. Chem., 254, p. 304. 



* Liebig's Ann. Chem., 260, pp. 289-306. 



" From cherry gum, Scheibler first obtained the arabinose (C'H'"0"). 



" Loco citato. 



' Berichte, 23, p. 1751 ; 24, p. 3575. 



* Journal of Analyt. and Applied Chem., Vol. V, No. 8, p. 421. 

 " Berichte, 24, p. 3579. 



