( 347 ) 
The presence of a soluble enzyme, capable of decomposing the 
glucoside, has not so far been proved with certainty '). 
The many attempts which have been made to separate such a 
soluble compound have so far given no result. On the other hand 
it was possible to show that the leaves contain, either a substance 
of this kind which is so firmly retained that it may be regarded as 
practically insoluble, or else they carry an insoluble substance which 
has the power of decomposing a solution of indican so that the sub- 
stance which on oxidation yields indigo, is set free. 
If indigoleaves are steeped in water for 7 hours and the sherry: 
coloured liquid, which contains the decompositionproduct which 
yields indigo on oxydation, is then displaced by distilled water con- 
taining chloroform, it is found that after several repetitions of this 
treatment, the displaced liquid yields no more indigo. The dried 
leaves are again washed several times with water containing chloro- 
form and then placed in contact with a solution of indican *) to 
which chloroform is added; after two hours this gives, when shaken 
with air, an abundant separation of indigo. If the leaves are now 
again thoroughly washed, they are still able to decompose a sterili- 
zed solution of indican. This may be repeated several times with 
the same leaves, even when they have been in contact with chloro- 
form water for more than a month. 
The washed leaves may be dried over sulphuric acid without 
losmg this property. 
The property of decomposing a solution of indican in an hour is 
retained after extracting the fresh leaves with ether, alcohol, acetone 
or chloroform. 
By treating the leaves, dried in this way, with dilute acids or 
bases or with glycerine, it has not sofar been possible to obtain 
") VAN LOOKEREN CAMPAGNE, Verslag omtrent onderzoekingen over Indigo, p. 13. 
contented himself with a reductio ad absurdum, a kind of proof which is somewhat 
unusual in researches of this nature. 
2) Such a solution of indican is prepared, according to ALVAREZ (C. R. 105, 287) 
by placing indigoleaves in small quantities at a time in boiling water. Quantitative 
ceterminations show that the decomposition of indican is very small when the time 
of contact is short. Mr, Loumayy, assistent for the examination of tea, found that 
such a solution of indican yields indigo in contact with emulsin and air; this agrees 
with older, vague statements that indican is decomposed by enzymes. The specimens 
of emulsin in the laboratory were insoluble in water. In the mean time it appeared 
from a publication of the Indigo-experimental-s tation at Klaten that Mr. HAZEWINKEL 
was experimenting with soluble enzymes in the preparation of indigo, this observation 
was therefore not followed further. (Note of 1897). 
