OF ARTS AND SCIENCES. 329 



There seemed no room for doubt that the chlorpyromucic acid thus 

 formed by the direct replacement of hydrogen by chlorine, like the 

 8 brompyromucic acid obtained in a similar way, contained its chlorine 

 in the 8 position. We considered it necessary, however, to establish 

 this point by direct experiment. 



Action of Bromine and Water. 



Although the action of bromine on 8 brompyromucic acid suspended 

 in water varied greatly with the conditions, Hill and Sanger* found 

 that, when the oxidation was carefully conducted, fumaric acid alone 

 was formed. We therefore suspended the 8 chlorpyromucic acid in 

 about twenty-five times its weight of water, and passed in bromine 

 vapor slowly with a current of air. The acid gradually dissolved, and 

 but little more than two molecules of bromine were needed to com- 

 plete the oxidation. After standing for some time in the cold, the 

 solution was evaporated to a small volume, and the crystalline acid 

 which appeared as the solution cooled recrystallized from hot water. 

 In this way we obtained a white crystalline acid which contained 

 neither chlorine nor bromine, which was sparingly soluble in cold 

 water, more readily in hot water, and which remained unchanged 

 when heated to 200°. Although the acid was thus sufficiently char- 

 acterized as fumaric acid, we further analyzed its silver salt. 



0.4943 grm. substance dried at 120° gave 0.5591 grm. AgBr. 



Calculated for 

 Ag,C 4 H 2 4 . Found. 



Ag 65.46 64.97 



In the oxidation of the 8 chlorpyromucic acid by bromine water, 

 fumaric acid, had therefore been formed according to the equation : 



C 5 H 3 C10 3 + 2 Br 2 + 3 H 2 = C 4 H 4 4 + CO a + 4 II Br + IIC1. 



Action of Nitric Acid. 



8 chlorpyromucic acid is not as readily attacked by nitric acid as the 

 8 brompyromucic acid, and for its complete oxidation we found it neces- 

 sary to heat one part of the acid with three parts of strong nitric acid 

 (Sp. Gr. 1.42) diluted with twice its weight of water. After heat- 

 ing for three hours the oxidation was completed, and on evaporation 

 fumaric acid was obtained, which was recognized by its sufficiently 

 characteristic physical properties. 



* These Proceedings, xxi. 144. 



