( 344 ) 
tion in concentrated sulphuric acid the nitration does not go further 
than the metamononitrocompound, so that the entry of the second 
nitro group must occur after the admixture of water. 
I pointed out previously (loc. cit) that the two dinitrocompounds 
may also be prepared by dissolving the metanitrocompound in an 
excess of very dilute nitrie acid. 
I now found that by dissolving 1 gram of metanitrodimethyl- 
anilme in a mixture of 26 grams of sulphuric acid and 50 grams 
of water, cooled to 30°, and adding 0.85 grams nitrie acid of 
50 pCt, a paste of the yellow dinitro-compound melting at 176° is 
obtained whilst, by means of sodium carbonate, the red isomeric is 
separated from the filtrate. These relative quantities are exactly those 
found in the liquid obtained by pouring the nitration mixture into 
the quantity of water prescribed. 
The small quantity of the dinitrodimethylaniline of Mertens which 
is produced shows that in nitrating dimethylaniline by the method 
of GROLL the meta-compound is formed almost exclusively in the con- 
centrated sulphuric acid solution and that the para-compound is most 
probably formed in the liquid after dilution with water by the action 
of unused nitric acid on dimethylaniline which has escaped nitration. 
When para-nitrodimethylaniline (L mol.) is dissolved in concen- 
trated sulphuric acid and 1 mol. of nitric acid is added to the solution, 
the dinitro-compound of Mertens is found alone after pouring the 
mixture into water; no nitro-group has taken up the meta position - 
with regard to the amino-group. 
Chemistry — “On the formation of Indigo from Indigoferas and 
from Marsdenia tinctoria”. By Dr. P. van Rompuren. 
(Communicated by Prof. A. P. N. FRANCHIMONT). 
The interesting communication which Prof. BEYERINCK made to 
the meeting of Sept. 30th last, from which it appears that the indigo 
yielding plants belong to two, physiologically quite distinct groups 
induce me to invite attention to some observations which I made 
some years ago during an investigation of indigo-yielding Indigoferas 
and of Marsdenia tinctoria which was published in the “Verslagen 
van ’s Lands Plantentuin’. I would add one remark. Owing to my 
other affairs I was unable to devote as much time to these resear- 
ches as I could have wished and they are therefore of a more or 
less preliminary nature. When I found, on the occasion of a mecting 
with Mr. HAZEWINKEL, Director of the Indigo Experimental Station 
