OF ARTS AND SCIENCES. 147 



From the barium salt we made the acid by exact precipitation with 

 sulphuric acid, and recrystallized it first from ether and afterwards 

 from water. The acid thus prepared melted at 131-132°,* was very 

 soluble in cold water, and by heating with hydrochloric acid in aqueous 

 solution was converted into an acid having all the physical properties 

 of fumaric acid. By the method just described we obtained about fifty 

 per cent of the weight of baric maleate theoretically required ; and since 

 the method of separation was necessarily imperfect, we have not hesi- 

 tated to assume that in the oxidation of 8-monobrompyromucic acid 

 with nitric acid maleic acid is the product first formed, and that 

 the fumaric acid obtained in the oxidation at higher temperature results 

 only from the further alteration of this. While we have been unable 

 to prove as yet the formation of maleic acid in the oxidation with 

 bromine, even under the most favorable conditions, it seems to us that 

 there can be little doubt that the reaction in this case is also essentially 

 the same. The occurrence of isodibromsuccinic acid among the pro- 

 ducts of the action of bromine, while it does not prove this view to 

 be correct, certainly is in its favor. 



/S-MONOBROMPYROMUCIC AciD. 



From either of the dibrompyromucic acids subsequently described 

 may be obtained by careful reduction a new monobrompyromucic acid 

 isomeric with that already described. Since the dibrompyromucic 

 acid melting at 167-168° is more conveniently prepared in large quan- 

 tity, we have used this in order to obtain material for investigation. 

 We have obtained the best results by dissolving two parts of the acid 

 in four parts of concentrated ammonic hydrate diluted with fourteen 

 parts of water, and adding one part of zinc dust. The reduction be- 

 gins at once, the solution becomes hot, and in a few minutes the reac- 

 tion is completed. When the ammoniacal solution no longer gives 

 with calcic chloride an immediate preci[)itate of the sparingly soluble 

 calcium salt of the dibrompyromucic acid, it is filtered and acidified 

 with hydrochloric acid. If the reduction has not been carried too far, 

 the solution soon solidifies with fine felted needles of the y8-monobrom- 

 pyromucic acid. For the purification of the acid we have found it best 

 to convert it into the calcium salt, and to reject that portion of the 



* Tlie melting-point of maleic acid is usually given as 130°, but Kc'kule' 

 lias recently given the higher melting-point 132°. — Ann. Chem. u. Pharm., 

 ccxxiii. 18G. 



