154 PROCEEDINGS OP THE AMERICAN ACADEMY. 



Reduction of Tetrabromdinitrohenzol. The tetrabromdinitrobenzol 

 was prepared essentially by the method given by Bancroft and one of 

 us * but a few improvements in the process should be mentioned here. 

 By usinc a large amount of glacial acetic acid the yield of tetrabrom- 

 benzol was materially raised. The details of this process will be 

 found in our paper, " On the Behavior of Certain Halogen Deriva- 

 tives of Benzol." In converting the tetrabrombenzol into the dinitro 

 compound we found that the quantities of sulphuric acid and nitric 

 acid used could be reduced to 50 c.c. of each for 10 grams of tetra- 

 brombenzol, if the tetrabrombenzol was pure ; if this was not the case 

 the best method was to treat the tetrabrombenzol with the acid mix- 

 ture, which had already been used once with tetrabrombenzol ; the 

 product of this action of the residual acid was then treated with one 

 half the amount of fresh sulphuric acid and nitric acid needed for the 

 complete conversion of the tetrabrombenzol into the dinitro compound, 

 and in this way a nearly pure product was obtained at little expense 

 of fuming nitric acid. With pure tetrabrombenzol the yield was very 

 nearly quantitative, 100 grams giving 121 grams of a product melting 

 at 220°, which after one recrystallization melted at 227°, the correct 

 melting point for tetrabromdinitrobenzol ; as 100 grams should give 

 122.8 grams, this makes the yield of this crude product over 99 per 

 cent. 



To reduce the tetrabromdinitrobenzol it was mixed with alcohol, 

 tin, and hydrochloric acid, and the mixture heated on the water bath 

 in a flask with a return condenser, more hydrochloric acid being added 

 from time to time. When the volume of liquid became unpleasantly 

 large, it was evaporated in an open dish to a convenient volume, and 

 returned to the flask with fresh alcohol and acid. After the organic 

 matter had gone completely into solution, which usually happened after 

 boilino' for about 70 hours, the liquid was again concentrated and ren- 

 dered strongly alkaline with crude sodic hydrate. The hydrate of tin 

 was filtered out with cheese cloth, and dried as thoroughly as possible 

 by sucking air through it, after which it was shaken repeatedly with 

 rather large amounts of alcohol. The alcoholic extract thus obtained 

 was freed from alcohol by distillation, followed by evaporation on the 

 water bath, when an oil and an aqueous solution were left, which were 

 separated, if possible, mechanically ; if not, by shaking with ether. 

 The oil obtained directly or from the ether solidified after a short 

 time. The aqueous filtrate from the hydrate of tin with the liquid 



* These Proceedings, XXIV. 289. 



