Dr. A. Schulte im Hofe 83 
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,”? 
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 Dev Tropenpflanzer, 1902, vol. ii, p. 92. 
