174 PROCEEDINGS OF THE AMERICAN ACADEMY 



Action of Nitric Acid. 



Dilute nitric acid oxidizes the /3y-dibrompyromucic acid readily on 

 heating. Carbonic dioxide is given off, and the solution then contains 

 mucobromic and dibrommaleic acids. Toennies's erroneous statement 

 that his acid was with difficulty oxidized even by strong nitric acid 

 was doubtless due to the fact that but little hydrobromic acid is formed 

 by the oxidation. For the complete oxidation of the acid we have 

 found two parts of strong nitric acid (sp. gr. 1.42) diluted with five 

 times its weight of water sufficient. After the reaction was over, we 

 extracted with ether and treated the white crystalline residue left on 

 evaporation of the ether with small quantities of cold water. The 

 sparingly soluble mucobromic acid was thus left undissolved, and its 

 identity proved by its melting-point (120-121°) and by analysis. 



0.2040 grm. substance gave 0.2967 grm. AgBr. 



Calculated for CiHoBrjOa. Found. 



Br 62.02 61.90 



The strongly acid aqueous solution was evaporated to dryness and 

 the residue again treated with a small amount of cold water, in order 

 to insure the removal of the mucobromic acid. The solution thus 

 obtained was neutralized with baric carbonate, the barium salt precipi- 

 tated with alcohol and recrystallized from water. The air-dried salt 

 then proved to contain a percentage of barium, agreeing with that 

 required by baric dibrommaleate. 



0.5138 grm. of the air-dried salt gave ou ignition with HgSO^ 0.2691 

 grm. BaSO^. 



Calculated for BaC^BroOi . 2 T3..0. Found. 



Ba 30.78 30.80 



The acid obtained from this barium salt was converted into its 

 anhydride by sublimation, and its identity with dibrommaleic anhy- 

 dride was shown by its melting-point, 114-115°. 



The oxidation of y8y-dibrompyromucic acid with dilute nitric acid 

 may therefore be expressed by the equations, 



C,Yi^^r.p, + 2 = C.H^BrPg + CO^. 

 C^H^Br^Oj -h 3 = C.HjBrp, + CO^. 



