OP ARTS AND SCIENCES. 139 



trichlorbenzol described in a previous paper.* Upon treating sym- 

 metrical tribrombenzol with a mixture of fuming sulphuric acid and a 

 nitric acid of specific gravity 1.51, but essentially free from nitrous 

 fumes, we found, as stated in the paper just mentioned, that tribrom- 

 trinitrobenzol was formed, thus confirming the results of Koerner, in 

 opposition to those of "VVurster and Beran ; and in the same place we 

 have tried to show that the most probable cause of the failure of these 

 latter chemists to obtain tribromtrinitrobenzol was the preseuce of a 

 large quantity of nitrous fumes in the nitric acid used by them, which 

 raised its specific gravity without increasing its strength. 



Tribromtrinitrobenzol, C 6 Br 3 (N0 2 ) 3 . 



Symmetrical tribrombenzol (melting point 119°) was converted 

 into tribromdinitrobenzol, either by treatment with nitric acid f of spe- 

 cific gravity 1.51, the mixture being warmed to secure complete ac- 

 tion, or by boiling it with a mixture of commercial fuming nitric acid 

 and common sulphuric acid. To convert the tribromdinitrobenzol, 

 by whichever process prepared, into tribromtrinitrobenzol, 20 grm. 

 of it were dissolved by the aid of heat in a mixture of about 500 c.c. 

 of the nitric acid of specific gravity 1.51 mentioned above with one 

 third of its volume of fuming sulphuric acid, since these proportions 

 had been found by experiment to give the best result with the least 

 consumption of acid, and the solution boiled gently in a flask loosely 

 closed with a glass bulb. As a portion of the nitric acid volatilizes 

 during the boiling, a little • >f the solid separates, which can be dis- 

 solved by the addition of m re nitric acid, but this precaution is not 

 necessary in working on a 1 'ge scale. When the mixture had boiled 

 for four to five hours, it w *rf allowed to cool, and then, disregarding 

 the comparatively large am mt of solid which had separated, poured 

 into snow, and the precipitate washed thoroughly with water and after- 

 ward purified, — first by extraction with hot alcohol, which removed 

 the unaltered tribromdinitrobenzol, since the tribromtrinitrobenzol is 

 but slightly soluble even in hot alcohol, — and then by crystallization 

 from chloroform, which separated the less soluble tribromtrinitro- 

 benzol from the tetrabromdiuitrobenzol X which was always formed at 



* These Proceedings, vol. xxii. p. 372. 



t Prepared directly from sulphuric acid and nitre, not pushing the reaction 

 beyond the formation of acid potassic sulphate. See our previous paper, 

 these Proceedings, vol. xxii. p. 372. 



i The purification and identification of this substance are described at the 

 end of this paper. If the tribromtrinitrobenzol is to be used in making triami- 



