220 PROCEEDINGS OP THE AMERICAN ACADEMY 



Action of Fuming Sulphuric Acid upon Tribrompyromucic 



Acid. 



After the experiments just described there could be little doubt as 

 to the action of fuming sulphuric acid upon tribrompyromucic acid. 

 We thought it worth while, however, to make a single experiment in 

 this direction. Tribrompyromucic acid dissolved readily in fuming 

 sulphuric acid, and decomposition quickly ensued at ordinary temper- 

 atures, so that the reaction was completed in the course of a day or 

 two. The diluted solution yielded, as the only product of the reaction, 

 dibrommaleic acid, which we recognized by the melting point of its 

 anhydride (114-115°), and by the analysis of its barium salt. 



0.5812 grm. of the air-dried salt gave 0.3063 grm. BaS0 4 . 



Calculated for 

 BaC 4 Br 2 4 . 2 H 2 0. Found. 



Ba 31.78 31.98 



Theoretical Considerations. 



The constitution of the various substances described in the preceding 

 pages requires but little discussion. The position of the sulpho-group 

 in the 8-sulphopyromucic acid is established not only by the formation 

 of fumaric acid by its oxidation, but also still more conclusively by its 

 formation in the reduction of /3y-dibrom-8-sulphopyromucic acid, to 

 which of necessity the formula 



BrC = C - COOH 



\ 

 O 



/ 

 BrC = C - S0 2 OH 



must be assigned. The close resemblance in structure of this acid to 

 dehydromucic acid, 



HC = C - COOH 



\ 



o 



/ 

 HC = C - COOH, 



is evident, and the formation of 3-nitropyromucic acid from dehydro- 

 mucic acid as observed by Klinkhardt,* finds its complete parallel in 



* Journ. pr. Chemie N. F., xxv. 41. 



