6 INTRODUCTION. 



and then succumb to consecutive oxidations, until after repeated cleav- 

 ages and oxidations the final products of metabolism are formed. 



An activation of the oxygen may be produced according to O. NASSE X by a 

 hydroxylization of the constituents of the protoplasm with the splitting off of 

 molecules of water. If benzaldehyde is shaken with water and air, an oxidation 

 of the benzaldehyde into benzoic acid takes place, while oxidizable substances 

 present at the same time may also be oxidized. The simultaneous presence of 

 potassium iodide and starch or tincture of guaiacum causes a blue coloration 

 because the hydroxyl (OH) takes the place of the hydrogen in the aldehyde group, 

 and these two hydrogen atoms, one derived from the aldehyde and the other 

 from the water, have a splitting action on the molecular oxygen. NASSE and 

 ROSING 2 have also found that certain varieties of protein have the property of 

 being hydroxylized in the presence of water. According to NASSE a whole series 

 of oxidations in the animal body may be accounted for by the oxygen atoms set 

 free in hydroxylization similar to that of benzaldehyde. In opposition to this 

 view we must remark that the oxidation of benzaldehyde to benzoic acid may also 

 take place in other ways, thus by the intermediary formation of a peroxide (see 

 BAEYER and VILLIGER; ENGLER and WEISSBERG 3 ). 



By quantitative methods, VAN'T HOFF and his pupils 4 have shown 

 that molecular oxygen can be divided in two parts by certain auto- 

 oxidation processes. One of these parts unites with the autooxidizer and 

 the other with a body simultaneously present but not directly oxidizable, 

 which, according to the suggestion of ENGLER, 5 is called the acceptor. 

 VAN'T HOFF claims that the oxygen molecule dissociates at ordinary 

 temperatures into minimum quantities of positively and negatively 

 charged oxygen atoms,' the ions of similar charge uniting with the 

 autooxidizable substance, while the remaining ions oxidize the acceptor. 

 Such a division of the oxygen into halves has also been shown by 

 other investigators, such as MANCHOT, ENGLER, and his collaborators. 6 

 These investigators nevertheless consider that autooxidation takes 

 place in another way, namely, by the formation first of peroxides by 

 the taking up of oxgyen molecules. 



TRAUBE 7 has also expressed a similar view. According to him, 

 in autooxidation we have to deal, in the first place, not with a cleavage 

 of the oxygen, but with a splitting of water in which the hydroxyl groups 

 of the water combine with the oxidizable substance, while the hydrogen 



1 O. Nasse, Rostocker Zeitung, No. 534, 1891, and No. 363, 1895. 



2 E. Rosing, Untersuchungen iiber die Oxydation von Eiweiss in Gegenwart von 

 Schwefel. Inaug. Dissert. Rostock, 1891. 



3 Baeyer and Villiger, Ber. d. d. chem. Gesellsch., 33; Engler and Weissberg, ibid., 33. 



4 van't Hoff, Zeitschr. f. physikal. Chem., 16; Jorissen, Ber. d. d. chem. Gesellsch., 

 30, and Zeitschr. f. physikal. Chem., 22; Ewan, ibid., 16. 



5 Ber. d. d. chem. Gesellsch., 33. 



6 Manchot, Ueber freiwillige Oxydation. Leipzig, 1900; Engler and Weissberg, 

 Ber. d. d. chem. Gesellsch., 33; Engler and Frankenstein, ibid., 34. 



7 Ber. d. d. chem. Gesellsch., 15, 18, 19, 22, and 26. 



