OP ARTS AND SCIENCES. 137 



formed by heating the tetrabromide had shown that a monobrom- 

 pyromucic acid couhl thus be formed, we attempted to prepare it by 

 heating the tetrabromide carefully in an oil bath. Although bromine 

 was set free together with hydrobromic acid and monobrompyromucic 

 acid was formed, we did not succeed in making the reaction available 

 for the preparation of this acid on a larger scale. If, on the other 

 hand, the bromine was allowed to act upon the pyromucic acid at the 

 outset at higher temperature, there was little difficulty in securing 

 abundant substitution and excellent product. At first we used glacial 

 acetic acid as a solvent to facilitate the reaction, but we afterwards 

 found that we could easily dispense with it, and that we could at our 

 jjleasure replace one or two hydrogen atoms in the pyromucic acid by 

 bromine by varying the conditions of the reaction. The monobrom- 

 pyromucic acid formed in this way melted at 183—184°, and appeared 

 to be identical with that already described by Schiff and Tassinari, 

 as far as could be judged from their meagre description, while the 

 dibrompyromucic acid was new and melted at 167-1G8°. 



In studying the action of alkalies upon the pyromucic tetrabromide, 

 we found that the product formed was a mixture of two isomeric 

 dibrompyromucic acids, one of which was identical with that formed 

 by the direct action of bromine upon pyromucic acid, while the second 

 melted at 190-191°, and was presumably identical with that which 

 Toennies had prepared in the same way, although he had not obtained 

 it in a state of perfect purity. While we have been wholly unable 

 to verify the assertion of SchifF and Tassinari, that a monobrom- 

 pyromucic acid exists, whose melting-point is 157°, we have found that 

 a new monobrompyromucic acid melting at 128—129° can be made by 

 the reduction of either of the two dibrompyromucic acids. We have 

 also found it a matter of no diificulty to prepare tribrompyroraucic 

 acid, either by direct substitution from one of the dibrompyromucic 

 acids, or by decomposing with alkalies the monobrompyromucic tetra- 

 bromide. 



These various substituted pyromucic acids are in many respects 

 more stable than pyromucic acid itself, and we have been able to de- 

 termine the relative position of the several bromine atoms through a 

 study of their oxidation products. 



8-MONOBROMPYROMUCIC ACID. 



Bromine acts upon pyromucic acid readily at 100° and forms a 

 monobrompyromucic acid. To insure a satisfactory yield we have 



