(516) 
KBr 0); a graphic representation was then made to show the results. 
These showed that the leaf (foliage without stems) may yield about 
0.60 per cent of indigo-blue which amounts to about 0.30 per cent 
in a plant containing 50 per cent of leaves. 
I must, provisionally, keep secret some other analytical processes 
of a more simple description. 
A closer study of the product which is formed during the fermen- 
tation on the large scale and also by the action of the enzyme on a 
solution of indican and which on oxidation yields indigo, taught me 
that this product consists of indoayl. 1) 
Then I found that the substance which on oxidation yields indigo, 
whether during the technical fermentation or by the action of the 
enzyme: 
1. is soluble in acids. 
2. is soluble in water, chloroform and ether. 
3. has a strong fluorescence. 
4. slowly forms indigo when exposed to the air in acid solutions, 
but rapidly in solutions having an alkaline reaction. 
5. changes into a red substance and emits a pungent odour when 
boiled with an acid. | 
6. yields indigo more readily when to the faintly acid solution a 
small quantity of ferric chloride is added. 
7. may get lost or modified to such a degree as to be incapable 
of yielding indigo, by the action of other constituents of the plant. 
This requires some further explanation. 
I prepared an alcoholic solution which one might call solution of 
crude chlorophyll in the following manner: 
Indigo leaves were crushed or rubbed with (20 pCt.) alcohol. By 
working quickly there was scarcely any danger of enzyme-action 
taking place. The turbid juice was filtered, the residue on the 
filter was taken up with water, again filtered and now extracted 
with alcohol. 
This alcoholic solution had the power to stop the formation of 
indigo in the fermentation liquid. This may be elegantly demon- 
strated in the following manner: 
") It is an interesting fact that BAUMANN and TrrMANN have suspected this to some 
extent. They wrote already in 1879 Ber. d. D. Chem. Gesell. 12 1103: „Bezüglich 
des Pflanzenindicans’ wird es nicht uninteressant sein zu ermitteln ob in demselben 
als Paarling Indoxyl oder Indigweiss, welche beide leicht in Indigo übergehen, vor- 
kommt und ob des im rohen Indigo enthaltene Indigroth in naher Beziehung zu dem 
Indoxyleondensationsproducte steht oder gar damit identisch ist.” 
"hat 
