Dr. A. Schulte im Hofe 8 



o 



with acid to produce this colour reaction. The 

 changes brought about in the bean by alcoholic 

 acetic fermentation may, therefore, also be 

 produced by the addition of acid. Fermenta- 

 tion is, therefore, not absolutely essential. By 

 means of it, however, the acidification is brought 

 about in the simplest and cheapest manner, 

 and the fleshy pulp adherent to the beans is 

 more or less completely removed. The beans, 

 having been treated with acid, were transferred 

 to a flask filled with oxygen. By the action 

 of the oxygen the bluish-violet colour gradually 

 changed to brown. When the acidified beans 

 were broken up and then treated with oxygen, 

 the process took place more rapidly. 



By the conversion of the bluish-violet colour 

 of the nibs into a brown one by means of 

 oxygen, it was proved that this process can 

 be brought about by chemical means. In the 

 same way I have proved that, at the same 

 time, as in the case of tea, the soluble astrin- 

 gent substances are converted into insoluble 

 ones. This I have already proved in the 

 manner described in my article on the "Culti- 

 vation and Manufacture of Tea in British India 

 and Ceylon," 1 



The above experiments prove that the 

 oxygen in the air acts on the acidified beans 

 in a manner similar to that in which it acts 

 on the tea-leaves after rolling. Since, how- 

 ever, the latter are specially prepared for this 



1 See Der Tropenpflanzcr, 1902, vol. ii, p. 92. 



