(343) 
twenty times its weight of concentrated sulphuric acid, and allowing 
2 mols. of nitric acid, also dissolved in sulphuric acid, to act on 
the solution so obtained at a low temperature and pouring the 
mixture onto ice. Different observations made during the often re- 
peated nitrations led me to doubt whether the dinitration really took 
place in the concentrated sulphuric acid solution, or whether, more 
probably, the reaction leading to the formation of the two nitropro- 
ducts took place in the mixture of acids when diluted with ice 
water. Further investigation of the course of the reaction actually 
brought to light that the nitration in concentrated sulphuric acid 
solution, even in presence of excess of nitric acid, does not go 
further than the formation of the mononitro-compound. 
If a cooled mixture of 104 gr. nitric acid of 50 pCt., or 60 gr. of 
86 pCt., and 300 gr. sulphuric acid be added in small quantities to a 
solution of 60 gr. dimethylaniline in 1 kg. of concentrated sulphuric 
acid, cooled to 0°, the temperature of the mixture rises at first 
with each addition. When half of the nitric acid has been added, 
however, no further rise of temperature is observed on adding the 
remaining half. When all the nitric acid has been added it is clear 
from the smell of the mixture that it contains free nitric acid. If, 
after half an hour, the half of the liquid is poured into 1'/, kg. of 
ice water (a mixture of equal parts of water and ice) the tempera- 
ture at the end of the experiment is 30° C., a yellow crystalline 
product (the dinitro-compound melting at 176°) is obtained and after 
addition of soda to the filtered acid liquid the red isomeric compound 
(melting point 112°). If a cooled solution of 25 grams of dimethyl- 
aniline in 2, kg. of sulphuric acid is added to the other half 
of the nitration liquid the rise of temperature is again clearly obser- 
vable. On pouring the mass, after some time, into 2'/, litres of 
ice water a mixture of para-and metanitrodimethylaniline with a 
little of Mr. Mertens’ 1. 2.4. dinitrodimethylaniline is obtained, such as 
is also produced according to Gror !) when dimethylaniline dissolved 
in concentrated sulphuric acid is nitrated with one molecule of 
nitric acid. 
When the nitration mixture containing one molecule of dimethyl- 
aniline and two molecules of nitric acid is poured into a mixture 
of ice and soda, dinitro-compounds are formed only in very small 
quantity or not at all. 
From these experiments it may be concluded that, in the solu- 
1) Berl. Ber. 19. 198. 
