JACKSON AND KOCH. — DERIVATIVES OF ORTHOBENZOQUINONE. 219 



As has just been stated, the crystallization of tetrabromorthobenzo- 

 quinone from glacial acetic acid cannot be effected without considerable 

 loss, which we found was due to the conversion of the tetrabromorthoqui- 

 none into two new bodies, one of which was red, the other white. * A 

 more careful study of the conditions under which the red body was 

 formed showed us that it was produced by the action of the orthoquinoue 

 with tetrabrompyrocatechine, either existing as an impurity in our tetra- 

 bromorthoquinoue, or formed from it by reduction. After this the study 

 of this red product was carried on with comparatively little difficulty. 



Preparation of Hexahromorthoquinopyrocatechirie Ether, Ci.2Br604. 



Eleven grams of tetrabroraorthoquinone and ten grams of tetrabrom- 

 pyrocatechine were dissolved in 470 c.c. of glacial acetic acid by heating 

 the mixture on the steam-bath, 180 c.c. of water were then added, which 

 produced no immediate precipitate, and the mixture allowed to stand in 

 a warm place for twenty-four hours. During this time a red precipitate 

 was formed, which was filtered out, and washed with hot alcohol to re- 

 move unaltered tetrabromorthoquinone and pyrocatechine. In tliis way 

 10.7 grams were obtained ; that is, somewhat over 60 per cent of the 

 theoretical yield. The purification of the substance offered at first some 

 difiiculty because it was insoluble in all the common solvents, but later 

 we found that it dissolved to a limited extent in hot nitrobenzol, and pro- 

 ceeded as follows : Two grams of the crude red body were dissolved in 

 150 c.c. of nitrobenzol by heating the mixture on the steam-bath (at 

 higher temperatures more of the substance will dissolve, but the solution 

 is attended with decomposition). Upon cooling, the solution deposited 

 about 0.7 gram of crystals, which were submitted to a second similar 

 crystallization from nitrobenzol at 100°, after which the product was 

 extracted several times with hot alcohol to remove adhering nitrobenzol, 

 dried at 100°, and analyzed. As the substance does not melt, we had 

 no means of determining whether this treatment had been an efficient 

 purification. 



I. 0.1809 gram of the substance gave on combustion 0.1374 gram of 



carbonic dioxide and 0.038 <jram of water. 

 II. 0.1008 gram of the substance gave by the method of Carius 0.1G37 

 gram of argentic bromide. 

 III. 0.1129 gram of the substance gave 0.1843 gram of argentic bromide. 



* Zincke (I'er. d. chem. Ges., XX. 1777) observed that acetic acid actcil oti tetra- 

 bromortlioquinone but did not isolate tlie products of tlie action. 



