JACKSON AND KOCH. — DERIVATIVES OF ORTHOBENZOQUINONE. 203 



body, which was soluble only in warm nitrobenzol. Its formula was 

 Ci2Br604, and it was formed by the following reaction : 



C6Br4(OH)o + CfiBrA = Ci2Br604 + 2HBr, 



as was shown by the detection of hydrobromic acid as one of the prod- 

 ucts of the reaction, and the fact that a good yield was obtained only 

 when the two reagents were used in equal amounts. This formation 

 of the substance is most naturally explained by supposing that the two 

 benzol rings are united together by two of the atoms of oxygen forming 

 a substituted pyrocatechine ether, C6Br^=0./C6Br202, but it is also possi- 

 ble that the union took place directly between the two benzol rings 

 forming a diyhenyl compound with this formula, OaBrgCe-CeBrgOs, the 

 two atoms of bromine removed in this reaction combining with the 

 atoms of hydrogen of the pyrocatechine, and thus oxidizing it so that 

 the body contains two orthoquinone groups. To decide between these 

 two formulas the substance was submitted to reduction with sodium 

 amalgam, as under these circumstances the pyrocatechine ether should 

 be split into two molecules of pyrocatechine, while the diphenyl com- 

 pound should be reduced without splitting the molecule. The princi- 

 pal product of this reduction was a chocolate brown substance, which 

 contained an amount of bromine nearly identical with that of the oriofi- 

 nal body, and was converted into it again by nitric acid. With it there 

 was always formed a certain amount of pyrocatechine, and this seemed to 

 us strongly in favor of the ether formula, but it could not be considered 

 conclusive, as the amount of pyrocatechine was much less than that of 

 the brown product. In the hope of increasing the yield of pyrocatechine 

 we submitted the brown product again to the action of sodium amalgam, 

 but found it was entirely unaffected ; we accordingly oxidized it to the 

 original red body, — a reaction which takes place quantitatively, — re- 

 duced this again by sodium amalgam, obtaining fresh quantities of pyro- 

 catechine and the brown body, and continued these alternate reductions 

 and oxidations until the original specimen of the red body had been 

 completely converted into pyrocatechine. Although we could wish that 

 this conversion had taken place by reduction alone, the use of the oxida- 

 tions cannot be held to vitiate the argument, as they gave a quantitative 

 yield of the original substance, and we feel justified, therefore, in infer- 

 ring that the two benzol rings are united by two atoms of oxygen, and 

 that the substance is a pyrocatechine ether. 



The brown product formed by the action of sodium amalgam was also 

 obtained by tbe action of tribrompyrogallol on the tetrabromorthoqui- 



