876 RESPIRATION AND OXIDATION. 



1. Iodides in acid solution in the presence of H 2 2 . According to BACH and 

 CHODAT l this reaction is completely parallel with the guaiac reaction. 



2. Formic acid with H 2 2 (see above). 



3. Amines (especially p-phenyldiamine) which forms colored products on 

 taking up oxygen. 2 



4. Leucobases or mixtures of their formers, which by oxidation are converted 

 into pigments. A solution of a mixture of a-naphthol and p-phenylen-diamine 

 made alkaline with soda gives indophenol on taking up oxygen (ROHMANN and 



SPITZER 3 ). 



5. Certain benzene derivatives which on oxidation and loss of water are 

 transformed into diphenol derivatives, for example vanillin into dehydrodi vanillin. 4 



For quantitative estimation of the extent of oxidation BACH and CHODAT 5 

 use the transformation of pyrogallol into purpurogallin, which latter can be weighed. 

 BACH 6 determines' the amount of iodine set free in the reaction between hydrogen 

 peroxide and hydriodic acid and BATELLI and STERN 7 determine the quantity of 

 C0 2 formed in the oxidation of formic acid. 



There is no doubt that reductions occur to a great extent in the animal 

 body and often go hand in hand with oxidations. The question as to 

 the extent in which special reduction enzymes are concerned, is still 

 undecided. As the oxidations are explained by the action of special 

 enzymes, so also we can admit of special reduction enzymes, so-called 

 reduclases or hydrogenases. To this group belongs the so-called " philo- 

 thion" (De REY-PAILHADE), which in the presence of sulphur and 

 water develops sulphuretted hydrogen, while others on the contrary do 

 not accept this view, and deny the enzyme nature of philothion. 8 The 

 investigations of NASSE and ROSING 9 on the oxidation of protein in the 

 presence of sulphur contradict the enzymotic nature of this formation 

 of sulphuretted hydrogen, and the recent investigations of HEFFTER 10 

 have shown that certain reductions occurring in the tissues are not pro- 

 duced by enzymes. He has also shown that those reductions, which are 

 not influenced fcy HCN, like the reduction of pigments (methylene blue), 



1 Ber. d. d. chem. Gesellsch., 35, 2466 (1902). 



2 Bioch. Zeitsqhr., 46, 317 (1912). 



Ber. d. d. phem. Gesellsch., 28, 567 (1894). 



4 In regard .to this and other reagents, see Zeitschr. f. physiol. Chem., 59, 359 

 (Engler and Herzog). 



5 Ber. d. d. chem. Gesellsch., 37, 1342 (1904). 

 Ibid., 37, 3785 (1904). 



^ Bioch. Zeitschr., 31/443; 33, 282 (1911). 



8 De Rey-Pailhade, Recherches expeY. sur le Philothion, etc., Paris (G. Masson), 

 1891, and Nouvelles recherches sur le Philothion, Paris (Masson), 1892; Bull. soc. 

 chim. (4), 1; Pozzi-Escot, Bull. soc. chim. (3), 27, and Chem. Centralbl., 1904, 1, 

 1645; Chodat and Bach, Ber. d. d. chem. Gesellsch., 36; Abelous and Ribaut, Compt. 

 Rend., 137, and Bull. soc. chim., (3), 31. 



9 E. Rosing, Unters. iiber die Oxydation von Eiweiss in Gegenwart von Schwefel, 

 Inorg.-Dissert, Rostock, 1891. 



10 Med.-naturw. Arch., 1, 81-104; Marburg, cited in Chem. Centralbl., 2, 1907, 

 822; Thunberg, Ergebn. d. Physiol., 11. 



