144 PROCEEDINGS OF THE AMERICAN ACADEMY. 



recrystallization from a mixture of alcohol and ligroine. or alcohol and 

 water, until it showed the constant melting point 212,° when it was 

 analyzed with the following results : — 

 I. 0.3036 gram of the substance gave by the method of Carius 0.3454 

 gram of argentic bromide. 

 II. 0.1945 gram of the substance gave 0.2239 gram of argentic bro- 

 " mide. 



Calculated for Found. 



C6HBr3(NHCOOC2H5)2. I. II. 



Bromine 49.08 48.42 48.99 



Properties. The tribromphenylene diurethane when deposited from 

 alcohol forms very small crystalline masses, which under the micro- 

 scope are seen to be rosettes made up of what at first sight appear to 

 be short needles, but on closer examination prove to be groups of 

 finer needles united longitudinally, since they betray their complex 

 nature by the frayed or brushlike appearance of their ends, which re- 

 semble a partially untwisted cord. Its color is white, and it melts at 

 212°. It is soluble in cold alcohol, easily soluble in hot ; easily soluble 

 in chloroform, or acetone, less so in ether ; somewhat soluble in cold 

 benzol, easily soluble in hot, from which it crystallizes in the same form 

 as from alcohol, but not so well; slightly soluble in carbonic disulphide 

 even when hot ; essentially insoluble in ligroine. Water dissolves it to 

 a very slight extent when hot. Hydrochloric acid produced no apparent 

 effect hot or cold ; sulphuric acid did not act on it in the cold, but when 

 hot dissolved it ; from this solution it seemed to be precipitated un- 

 changed by water, if the heating had not been long continued, but long 

 heating with the strong acid decomposed it. A concentrated solution 

 of potassic hydrate seemed to have no effect on it in the cold, but when 

 heated turned the substance brown, and finally black with apparently 

 complete decomposition. The best solvent for it is alcohol diluted 

 with either water or ligroine. 



Reduction of Trihromdinitrohenzol. 



Tribromdinitrobenzol (melting at 192°, made from symmetrical 

 tribrombenzol) was reduced by treatment either with zinc and acetic 

 acid, or with tin and hydrochloric acid, but the products were different 

 in the two cases as described in the following sections. 



Red^tction with Zinc Dust and Acetic Acid. This reduction we 

 found it best to carry on in an atmosphere of carbonic dioxide, as the 

 liquid showed a strong tendency to turn black during the process. 



