132 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The somewhat high result may be due to a trace of a substance con- 

 tainingr iodine. If the mixture of tribromiodbenzol and funaius nitric 

 acid was boiled, the organic product was the same, but no free iodine 

 was obtained. 



Behavior of Unsymmetrical Tetrabromhenzol melting at 98°. 



The action of sodic ethylate on this substance was selected for 

 study, because that reagent had given the best results in the work on 

 tribromiodbenzol just described. To prepare the unsymmetrical tetra- 

 bromhenzol, 20 grams of tribromaniline were dissolved in 180 c.c. of 

 hot glacial acetic acid, about 80 c.c, that is a considerable excess, of a 

 distilled solution of liydrobromic acid (boiling point 125°) added, and, 

 disregarding any precipitate formed, the mixture treated with sodic 

 nitrite in the proportion of a molecule and a half or two molecules to 

 each molecule of the tribromaniline. For this purpose the finely pow- 

 dered nitrite was slowly sifted with vigorous stirring into the solution, 

 which had previously been cooled so that it felt barely warm to the 

 hand. The white crystals which were suspended in it gradually 

 changed into a dirty brown solid, much of which dissolved even in the 

 cold. The mixture was then heated for two or three hours on the 

 water bath ; the solid matter at first went into solution, but later 

 the tetrabromhenzol, as it formed, separated, principally in long white 

 needles, or sometimes in part as a serailiquid brown mass. The needles 

 were separated mechanically, and were usually found to be pure. The 

 semiliquid portion solidified in a short time, and was purified by dis- 

 solving it in a little hot benzol, and pouring this solution into alcohol. 

 The tetrabromhenzol precipitated in this way had a slight reddish 

 color, while the mother liquor was of a dark claret-red. The precipi- 

 tate was easily obtained white by one or two recrystallizations from a 

 large volume of alcohol, to which it was well to add a little benzol. 

 In this way 20 grams of the tribromaniline gave 22 grams of tetra- 

 bromhenzol, instead of the 23.88 grams required by the theory, a yield 

 of 92 per cent. 



Eio'ht erams of the tetrabromhenzol were mixed with an alcoholic 

 solution of sodic ethylate, made from 2 grams of sodium and 50 c.c. 

 of absolute alcohol, and a little benzol to assist the solution of the 

 tetrabromhenzol. The mixture was heated to boiling under a reverse 

 condenser for two days, when it had taken on a blackish green color ; 

 it was then evaporated to dryness, and washed with water. The 

 wash waters gave a good test for sodic bromide. The residue insol- 

 uble in water was sublimed at the lowest possible temperature, when a 



