OP ARTS AND SCIENCES. 373 



and the diuitro compound are new, the difficulty of the preparation of 

 symmetrical trichlorbeuzol having prevented a thorough study of this 

 substance. On the other hand, the corresponding tribrombenzol can 

 be made with great ease, and, as its action with fuming nitric acid has 

 been studied frequently, we decided to extend our experiments to it to 

 see whether in this case also our nitric acid proved more reactive than 

 that of the chemists who have worked in this field heretofore. The 

 complete description of our results with tribrombenzol will be post- 

 poned till a later paper, and we shall give here only that portion of 

 them which shows that the action of our nitric acid on the tribrom- 

 benzol is similar to its action on the triclilorbenzol, prefacing it with 

 a brief historical sketch of the work of our predecessors. 



Koerner* was the first (in 1874) who studied this subject, obtain- 

 ing on dissolving the symmetrical tribrombenzol with the aid of heat 

 in nitric acid of specific gravity 1.54 the dinitro compound, with a 

 mixture of fuming sulphuric acid and nitric acid the trinitro com- 

 pound, while all his attempts to obtain the raononitro derivative by 

 direct nitriring failed, owing to the insolubility of the tribrombenzol in 

 weaker acid. In the next year f one of us | working in the laboratory 

 of Berlin found that the fuming nitric acid supplied in that laboratory 

 converted tribrombenzol into the mononitro compound only when 

 boiled with it, and that it was necessary to use a boiling mixture of 

 nitric and (common) sulphuric acids to obtain the dinitro deriva- 

 tive. These observations were confirmed a few years later by Wurster 

 and Beran,§ who obtained only the mononitro compound from the 

 action of a nitric acid of 1.534 specific gravity alone, and the dinitro 

 compound when its action was reinforced by mixture with crystallized 

 fuming sulphuric acid. Even when this mixture was heated with 

 tribrombenzol in sealed tubes to 220° for 48-60 hours, only a very 

 minute quantity of a trinitro compound was formed ; which led them 

 to the conclusion that the trinitro derivative mentioned but not 

 described by Koerner could not be obtained. 



In taking up again the study of the nitro compounds of symmetrical 

 tribrombenzol we used the nitric acid of specific gravity 1.505-1.51, 



* Gazz. Chim., iv. 422, 425. 



t Von Richter (Ber. d. ch. G., 1875, p. 1426) succeeded in obtaining the mono- 

 nitro compound by boiling glacial acetic acid and tribrombenzol with nitric 

 acid of specific gravity 1.52, but found, in agreement with Koerner, that an acid 

 of 1.54 boiled with tribrombenzol converted it into tlie dinitro compound. 



t Jackson, Ber. d. ch. G., 1875, p. 1172. 



§ Ber. d. ch. G., 1879, p. 1821. 



