290 PROCEEDINGS OF THE AMERICAN ACADEMY 



until the proportion of the total sodic nitrite to the tribromaniline was 

 three molecules to one (this very large excess of sodic nitrite being 

 found necessary to complete the reaction). The liquid on cooling 

 deposited a tarry mass, which was extracted repeatedly with small 

 quantities of hot alcohol, until it was converted into crystals (melting 

 at about 95°). An additional amount of these crystals was obtained 

 by pouring into water the red liquid from which the tar had been 

 deposited, but this amount was not large. The product, after purifica- 

 tion by one or two crystallizations from hot alcohol, showed a yield of 

 from 89 to 93 per cent of the theoretical. 



To convert the tetrabrombenzol into tetrabromdiuitrobenzol, 10 grs. 

 of it were dissolved with the aid of heat in nitric acid of specific 

 gravity 1.52, prepared in the laboratory from nitre and sulphuric acid ; 

 then the same volume of strong sulphuric acid was added, about 200 c.c. 

 of the mixture of the two acids being used, and, after standing in the 

 cold for ten minutes, the whole was boiled for about an hour in a flask 

 closed with a glass bulb. If the tetrabrombenzol was sufficiently pure 

 there was little foaming and no violent action, and on cooling a white 

 crystalline solid separated, which was nearly pure tetrabromdiuitro- 

 benzol, and, after crystallization from benzol with a little alcohol, or 

 from chloroform, showed the right melting point 228°.* 



If, on the other hand, a tetrabrombenzol was used containing some 

 of the impurity already mentioned, which, when present in quantity, 

 lowered the melting point to the neighborhood of 87°, the action was 

 .violent, the boiling being accompanied by much foaming, the product 

 was often oily, and, after most of the solid had been precipitated by 

 water, the aqueous liquid contained decomposition-products, as was 

 shown by the blackish precipitate formed in it on the addition of sodic 

 carbonate. The main product in this case was a mixture of the tetra- 

 bromdiuitrobenzol and another substance, which was obtained by 

 treatment with aniline or sodium malonic ester, and subsequent sep- 

 aration of the derivative of the tetrabromdiuitrobenzol by crystalliza- 



* One of us and J. F. Wing (These Proceedings, xxiii. 148) some years 

 ago obtained tetrabroradinitrobenzol as a secondary product in the manufacture 

 of tribroratrinitrobenzol, but we were unable to raise its melting point above 

 224°; this was ascribed at the time to the presence of a little tribromtri- (or di-) 

 nitrobenzol, an opinion which is confirmed by the fact mentioned above that 

 tetrabromdinitrobenzol prepared by us according to the usual method showed 

 the melting point 228° given by Von Richter (Ber. d. ch. G., 1875, p. 1427). The 

 difficulty in removing the tribrom compound can be accounted for by supposing 

 tliat it forms the addition-product observed by one of us and G. D. Moore (Ber. 

 d. ch. G. 1888, p. 1707), or an analogous one with the trinitro compound. 



