OF ARTS AND SCIENCES. 341 



formed rhombic plates separated which were dried over sulphuric 

 acid for analysis. 



0.2233 grm. substance gave 0.3433 grm. AgCl. 



Calculated for 

 C 4 U 2 C1 2 4 . FouDd. 



CI 38.38 38.01 



The identity of this acid with dichlormaleic acid was further de- 

 termined by the melting point of the anhydride prepared by sublima- 

 tion, which we found to be 119-120°, in agreement with the statement 

 of Ciamician and Silber.* 



The oxidation therefore took place in accordance with the following 

 reactions, 



C 5 H 2 C1 2 8 +20= C 4 H 2 CI 2 8 -f C0 2 , 

 C 5 H 2 C1 2 3 +30 = C 4 H 2 C1 2 4 + C0 2 , 



and the dichlorpyromucic acid in question is thus conclusively shown 

 to have its chlorine atoms in the j3 and y positions. 



Preparation of Isomeric Dichlorpyromucic Acids. 



Although we had been unable to find the (38 dichlorpyromucic acid 

 among the products formed by the action of alkalies upon ethyl 

 pyromucic tetrachloride, it seemed to us probable that it might be 

 formed under the proper conditions by the direct action of chlorine 

 upon ethyl pyromucate, or by the decomposition of its tetrachloride by 

 heat alone. 



Tunnies f had already shown that 8 brompyromucic acid could be 

 formed by heating pyromucic tetrabromide, and Hill and Sanger $ had 

 further shown that 8 brompyromucic acid and /38 dibrompyromucic 

 acid could conveniently be made by the action of bromine upon pyro- 

 mucic acid at high temperature. As subsequent experiments in this 

 laboratory had shown that these two acids could more advantageously 

 be made by substituting the ethyl ether for the acid, and our own 

 experiments had shown that the S chlorpyromucic acid could readily 

 be made in this way, we proceeded to study the action of chlorine 

 upon ethyl pyromucate at high temperature. It seems hardly neces- 

 sary to describe in detail the numerous experiments which we made 

 under widely varying conditions, each one of which yielded us purely 

 negative results. Ethyl pyromucate was treated with chlorine at 



* Berichte d. deutsch. chem. Gesellscb., xvi. 2390. 



t Ibid., xi. 1088. 



| These Proceedings, xxi. 130, 100. 



