160 PROCEEDINGS OF THE AMERICAN ACADEMY 



ever, be more conveniently, if not more economically, prepared by the 

 direct action of bromine upon pyromucic acid. The reaction is appar- 

 ently quite complex, a large excess of bromine is required, and the 

 product is small compared with that theoretically required. Pyro- 

 mucic acid is treated with about three molecules of bromine, and heated 

 on the water bath with reverse cooler, until the evolution of hydro- 

 bromic acid is over. There remains, then, in the flask a red viscous 

 oil which contains /3S-dibrompyroraucyl bromide with a small amount 

 of 8-monobrompyromucyl bromide, dibrommaleic acid or its anhydride, 

 and other products not yet moi'e exactly determined. This oil is washed 

 with cold water to remove the more soluble products, and is then 

 boiled with water until the acid bromides are converted into the acids. 

 The separation of the dibrompyromucic from the monobrompyromucic 

 acid with which it is mixed may be most conveniently effected by 

 precipitating its barium salt from an ammoniacal solution by the addi- 

 tion of baric chloride, and repeating the operation until a product 

 melting at 165-1G6^ is obtained. By subsequent recrystallization 

 from hot water and from benzol the melting-point may then be raised 

 to 167-1G8°. 



The acid thus purified gave, on analysis, the following results : — 



I. 0.5370 grm. substance gave 0.4379 grm. C0._2 and 0.0390 grm. 



11,0. 

 II. 0.2251 grm. substance gave 0.3125 grm. AgEr. 

 III. 0.1 GG5 grm. substance gave 0.2323 grm. AgBr. 



m. 



59.39 



The yeS-dibrompyromucic acid is readily soluble in alcohol or ether, 

 freely soluble in boiling chloroform, quite readily soluble in benzol, 

 but sparingly soluble in carbonic disnlphide or ligroin. It is sparingly 

 soluble in cold water, quite readily soluble in boiling water, and crys- 

 tallizes on cooling in small oblique prisms, which, however, usually 

 appear in characteristic twinned forms. 



The solubility of the acid in water at ordinary temperatures we 

 determined by neutralizing with baric carbonate the saturated solution, 

 and determining by precipitation with sulphuric acid the amount of 

 barium dissolved. 



