OP ARTS AND SCIENCES. 205 



aqueous solution of the barium salt, baric sulphate is at once precipi- 

 tated, and after the reaction is completed by gentle heat ether extracts 

 from the filtered solution dibrommaleic acid. The anhydride formed 

 by sublimation was found to melt at the proper point, 114-115°. 



Action of Nitric Acid. 



Diluted nitric acid oxidizes /3y-dibrom-S-sulphopyromucic acid on 

 beating and forms dibrommaleic acid, whose identity we established 

 through the melting-point of its anhydride, 114—115°. By the action 

 of fuming nitric acid a nitro-acid is formed. The dry acid was slowly 

 added to several times its weight of fuming nitric acid. At first the 

 mixture was cooled, afterwards warmed and the greater part of the 

 nitric acid then expelled by gentle heat. The crystalline product of 

 the reaction was in part an acid quite readily soluble in hot water, and 

 in part a neutral substance which dissolved with more difficulty in 

 boiling water. For the complete separation of these two substances 

 we treated the product with a dilute solution of sodic carbonate and 

 extracted with ether. The alkaline solution was then acidified and 

 the acid extracted with ether. After several recrystallizations from 

 hot water, it formed finely felted yellow needles, which were sparingly 

 soluble in cold water, more readily in hot, and melted at 204-205°. 

 They dissolved freely in alcohol, ether, or in benzol. Analysis showed 

 the substance to be a dibromnitropyromucic acid. 



I. 0.1050 grm. of the acid gave 0.1260 grm. AgBr. 

 II. 0.2970 grm. of the acid gave 11.7 c. c. of moist nitrogen at 21° 

 under a pressure of 758 mm. 



Calculated for 

 C HBr 2 (N0 2 )0 3 . Found. 



Br 50.79 51.07 



N 4.44 4.47 



The mode of its formation shows that this acid must of necessity be 

 the j3y-dibrom-S-nitropyromucic acid. 



The ether which had been used for extracting the alkaline solution 

 of the crude nitro product left, on evaporation, a quantity of a yellow 

 crystalline solid, which was sufficient to enable us to establish its iden- 

 tity by analysis. The substance was sparingly soluble even in hot 

 water, and crystallized on slow cooling in stout prisms, or on rapid 

 cooling and scratching in felted needles. In alcohol it was sparingly 

 soluble ; but benzol dissolved it freely, and on standing the solution 

 deposited quite large transparent yellow prisms, which effloresced rap- 



