218 PROCEEDINGS OF THE AMERICAN ACADEMY. 



and, as a comparison of the two substances showed they crystallized in 

 the same form, there can be no doubt of their identity. The formation 

 of a paraquinoue derivative from our orthoquinone has been already 

 explained in the introduction to this paper. 



In the hope of obtaining a phenaziue the solution of orthoquinone was 

 treated with orthophenylene diamine ; a reaction took place, tlie principal 

 products of which consisted of uninviting black substances and pyrocate- 

 chine recognized by the formation of its lead salt. From the appearance 

 of the pyrocatechine we inferred that the reaction consisted principally 

 in the oxidation of the diamine by the orthoquinone, and as even after 

 trying the experiment under several varying conditions no more prom- 

 ising results were obtained, this line of work was abandoned. Phenol 

 also gave with the solution of orthoquinone such an uninviting product 

 that we did not attempt to study it. Sodic hydrate gives with the ortho- 

 quinone solution a green coloration similar to that obtained by the action 

 of sodic hydrate on tetrabromorthoquinoue. 



Derivatives of Trtrabkomorthobenzoquinone. 



The tetrabromorthoquinoue used in this work was prepared as follows : 

 20 grams of pyrocatechine were dissolved in 50 c.c. of glacial acetic 

 acid, and 37 c.c. of bromine added gradually from a burette. The mix- 

 ture was allowed to stand over night, after which the product was puri- 

 fied by recrvstallization from 200 c.c. of glacial acetic acid. In this way 

 forty grams of pyrocatechine yielded 118-126 grams of recrystallized 

 tetrabrompyrocatechine ; that is, between 75 and 80 per cent of the theo- 

 retical yield. To convert this tetrabrompyrocatechine into tetrabrom- 

 orthoquinoue thirty grams of it were dissolved in 300 c.c. of glacial acetic 

 acid by heating on the water-bath ; the solution was then cooled to 16°, 

 or until the glacial acetic acid began to solidify, and eleven grams of 

 fuming nitric acid of specific gravity 1.5 diluted with 60 c.c. of glacial 

 acetic acid added rapidly, the mixture being kept cool and stirred vig- 

 orously daring the addition ; after standing for five minutes 300 c.c. of 

 water were added, and stirred in thoroughly. If the jji'ocess had run 

 successfully, the tetrabromorthoquinoue settled to the bottom in a glis- 

 tening mass of dark red crystals, which were filtered ofi^, and dried. The 

 product thus obtained melted at 14o°-147° instead of 150°-151°, but 

 was pure enough for our work, which was fortunate, as recrystallization 

 from glacial acetic acid is attended by a great loss of material. Thirty 

 grams of tetrabrompyrocatechine gave eighteen grams of tetrabromortho- 

 quinone, which amounts to about 60 per cent of the theoretical yield. 



