FIXATION OF ATMOSPHERIC NITROGEN 573 



gas and nascent hydrogen with which it comes into contact. The hydro- 

 gen is formed in the butyric acid fermentation of the organism. The 

 ammonia is immediately assimilated and is converted into protein. 50 

 The actual assimilation of the nitrogen may take place according to the 

 following reactions: 51 



2 NH 3 + 2 C0 2 + H 2 -» 2 H • CO • NH 2 + H 2 + 2 



formamide 



2 H • CO • NH 2 + H 2 -> COONH 4 + H 2 -» COO • NH 4 + |(O a ). 



CO • NH 2 CH 2 • NH 2 



It has also been suggested 52 that the fixation of nitrogen by Azotobacter 

 takes place by reduction by means of hydrogen with the formation of 

 cyanides as intermediary products. Wieland 53 considered that the ac- 

 tion of the hydrogen acceptors formed in the cells of nitrogen-fixing 

 bacteria does not depend upon oxygen for hydration, but upon the 

 molecular nitrogen with which it forms ammonia, perhaps through the 

 hydrazine stage in a manner similar to the Haber synthesis. 



The fixation of nitrogen by an oxidation process, similar to nitro- 

 gen-fixation in moist air through the oxidation of organic matter, has 

 also been suggested. 54 The nitrogen is believed to be first oxidized to 

 N 2 3 with iron hydrate as a catalyst; the nitrous acid may then be 

 assimilated by the organism. 55 It has also been suggested 56 that am- 

 monium nitrite is first synthesized. However, neither nitrate nor 



60 Kostytschew, S., and Ryskaltshouk, A. Les produits de la fixation de 

 1'azote atmosphyrique par V Azotobacter agile. Compt. Bend. Acad. Sci., 180: 

 2070-2072. 1925; Ztschr. physiol. Chem., 154: 1-17. 1926. 



61 Loeb, W. tlber das Verhalten des Formamids unter der Wirkung der stil- 

 len Entladung. Ein Beitrag zur Frage der Stickstoff- Assimilation. Ber. deut. 

 chem. Gesell., 46: 684-697. 1913. 



62 Stoklasa, 1908 (p. 562). 



63 Wieland, H. tlber den Verlauf der Oxydationsvorgiinge. Ber. deut. chem. 

 Gesell., 55: 3639-3648. 1922. 



64 Gautier, A., and Drouin, R. Becherches sur la fixation de 1'azote par les 

 sols et les vegetaux. Compt. Bend. Acad. Sci., 106: 754-757, 863, 944, 1174, 

 1232, 1605. 1888; 113: 820-825. 1891 ; also Berthelot, 1892 (p. 558). 



65 Bonnema, A. Gibt es Bakterien, die den freien N assimilieren oder ist dies 

 ein chemischer Frozesz? Chem. Ztg., 27: 148. 1903; Centrbl. Bakt. II, 10: 

 598-602. 1903. 



66 Czapek, F. Der Stickstoff im Stoffwechsel der Fflanze. Ergeb. Physiol. 

 I, 2: 638-672. 1903; Heinze, B. Centrbl. Bakt. II, 12: 364. 1904. 



