( 520 ) 
It is known that indoxyl possesses both week acid and basic 
properties. This has been recorded by A. v. BAYER who noticed 
the week acid and basic properties of indexyl prepared from indoxylic 
acid, therefore, presumably a very pure product. If now the indoxyl 
should be partly combined with lime, the oxidation must cause a 
loss of acidity. 
The acidity is also bound to become less by the gradual disappear- 
ance of the free CO, which is always formed during the technical 
fermentation and in the laboratory experiment. This fully explains 
the reason why the liquid gradually changes from the acid to an 
alkaline condition. Finally, I wish to call attention to the following 
point: If a solution of indican is prepared by crushing the leaves 
with lime-water and filtering the neutralized liquid, and when to 
this is added a perfectly neutral solution of enzyme, a solution of 
indican is finally obtained which yields no indirubin with isatin and 
sodium hydroxide. If the solution is oxidated in a current of air free 
from COs, the filtrate is distinctly alkaline. It is, therefore, plain 
that indican forms a neutral saline compound, which is decomposed 
like free indican by indimulsin (somewhat analogous to myronic 
acid and its potassium salt). 
Klaten (Java), Jan. 1900. 
Chemistry. — Prof. S. HooGEWERFF presents a communication, 
also on behalf of Mr. H. reR MEULEN, entitled: “Contri- 
bution to the knowledge of indican”’. 
Observations made lately by BEIJERINCK!) and HAZEWINKEL ”) on 
indican have shown that this substance is not so readily decomposed 
as was formerly believed ®). It is not decomposed by evaporating its 
aqueous solution, but on the contrary, if free acids and enzymes 
are absent, it possesses a fair degree of stability and a solid mass 
of “crude indican” may be obtained by evaporating the decoctions 
of Indigofera leptostachya and Polygonum tinctorium *). 
It was only natural that these important observations should lead 
to an effort to obtain the indican on a pure condition and to deter- 
mine its composition. The formula Cys Hs; NOj, proposed by 
SCHUNCK ®) as the result of investigations which are in many respects 
1) Proc. Royal Acad. of Sc. Amsterdam, Sept. 1899 p. 91. 
*) See preceding article. 
3) Scuunck Phil. Mag. [4} X p. 78 and [4] XV p. 29, 117, 183. 
4) BEYERINCK |. c. p. 95. 
