OF ARTS AND SCIENCES. 183 



The identity of the dibrommaleic acids made by the action of dry 

 bromine upon mucobromic acid and aqueous bromine upon succinic 

 is thus sufliciently established. They each give an anhydride melt- 

 ing at 114—115°; their barium salts have the same composition, 

 BaC^Br.,0^.2II.,0 ; and the solubility of these two salts in water is the 

 same, the saturated aqueous solution containing in one case 5.66 per 

 cent of the anhydrous salt at 19°, in the other 5.71 per cent at 20°. 



Although I have several times tried the action of bromine and 

 water upon mucobromic acid, according to the method of Limpricht 

 and Delbriick, I have not as yet submitted the product obtained in 

 this way to any very extended investigation. In all qualitative reac- 

 tions it is identical with the acid I have described ; and, considering 

 the mode of its formation, one can hardly doubt its identity. More- 

 over, with regard to the slight differences which would seem to have 

 induced Limpricht and Delbriick to consider their acid isomeric with 

 Kekule's, I have been unable to confirm their observations. The 

 melting point (95-120°) given by them for the anhydride does not 

 give confidence in the purity of their material. The higher percent- 

 age of barium (31.9) * which they found in their barium salt would 

 be in no way at variance with my results, even if its purity were 

 granted, since the material they analyzed had been dried in vacuo 

 (over sulphuric acid ?), and my own experiments have shown that it 

 slowly effloresces under these conditions. 



Although the foregoing facts seemed to warrant the conclusion 

 that the dibrommaleic acid of Kekule belonged to the maleic series, 

 inasmuch as the anhydride was the direct product of the reaction of 

 bromine upon mucobromic acid, still I thought it advisable to prove 

 this directly, more especially since all analogy pointed to the forma- 

 tion of a derivative of fumaric acid under the conditions essential to 

 its preparation from succinic acid. I therefore dissolved in water the 

 pure anhydride prepared from succinic acid, neutralized the solution 

 with baric carbonate, precipitated the barium salt by alcohol, and 

 recrystallized it from water. This salt proved to be identical with 

 that which was obtained directly from the acid. 



0.7525 grm. of the air-dried salt lost on heating to about 120° 0.0581 

 grm. ; 0.6933 grm. of this dried salt gave 0.3922 grm. BaSO^. 



* Limpricht and Delbriick erroneously calculated tlic percentage of barium 

 in the salt BaC4Br204.2H20 as 31.9 per cent, instead of 30.78, and therefore 

 gave the same formula. 



