146 PROCEEDINGS OF THE AMERICAN ACADEMY. 



flask closed by a cork provided with a Bunsen valve, until the greater 

 part of the air had been expelled. 10 grams of tribromdinitrobenzol 

 mixed with enough alcohol to make a thick paste were then added, and 

 the reduction was allowed to go on, warming or cooling the mixture as 

 was necessary, until all the organic substance had dissolved. If the solu- 

 tion thus obtained was a strong one, beautiful white needles of a double 

 tin salt were deposited on cooling ; if it was more dilute, they usually 

 appeared after standing a day, but in some cases the substance obsti- 

 nately refused to crystallize. The crystals were filtered out, and de- 

 composed in concentrated solution with sulphuretted hydrogen, when 

 the filtrate from the sulphide of tin left on evaporation a crystalline 

 solid which after three crystallizations from a mixture of water and 

 hydrochloric acid was analyzed with the following results. 

 I. 0.2220 gram of the substance gave 31.8 c.c. of nitrogen at a tem- 

 perature of 26.5° and a pressure of 756.9 mm. 

 II. 0.2983 gram of the substance gave by the method of Carius 0.4727 

 gram of argentic chloride. 



Nitrogen 

 Chlorine 



The tin and hydrochloric acid had therefore reduced both the nitro 

 groups, and also removed all three of the atoms of bromine from the 

 tribromdinitrobenzol ; and that the removal of bromine had taken 

 place from the whole of the substance was made probable by the fact 

 that all the organic matter dissolved, whereas the tribroraphenylene 

 diamine, as already stated in this paper, is insoluble in water or 

 dilute hydrochloric acid. An additional confirmation of the presence 

 of phenylene diamine was given by the following experiment. The 

 base set free from the soluble chloride analyzed above was treated 

 with bromine water, when a precipitate was formed, wliich after recrys- 

 tallization from alcohol containing a little benzol melted at 158°, and 

 was therefore the tribroraphenylene diamine which is made in this way 

 from metajjhenylene diamine. 



^Yhen we began work on this subject we made many analyses of the 

 double tin salt which crystallized out of the solution after the reduc- 

 tion ; but although in two different preparations we obtained numbers 

 agreeing with the salt C6H4(NH3ClSnCl2)2 discovered by Gudemann,* 

 we found that in others its composition varied so much that no certain 



* Zeitsch. fiir Cliem. 1865, p. 51. 



