2 PROCEEDINGS OP THE AMERICAN ACADEMY. 



dered a detailed study of it impossible. While the chlorine derivative 

 was more accessible, it was not more carefully studied by Hill and 

 L. L. Jackson since it was discovered only at the close of their inves- 

 tigation of the chlorpyromucic acids. They were also but partially 

 successful in determining the constitution of the ^-dichlorpyromucic 

 acid from which it was so easily formed. They showed that one 

 chlorine atom of this acid was in the 8 position, but could bring for- 

 ward no definite facts to prove whether it was a /38-dichlorpyromucic 

 acid stereometrically isomeric with the common form, or whether it 

 was the third possible structural isomer, the -yS-dichlorpyromucic acid. 

 In the former case its ready decomposition by aqueous hydrochloric 

 acid might be due to its peculiar configuration, in the latter case this 

 reaction might be conditioned by the simultaneous presence of halogens 

 in the y and 8 positions. If the instability of the 'acid were due to the 

 positions occupied by the halogen atoms, it seemed probable that the 

 tri-substituted pyromucic acids which also contain halogen in the y and 

 8 places would show the same behavior. Although Hill and Sanger 

 had observed no such decomposition in studying tribromjDyromucic 

 acid, and Hill and L. L. Jackson noticed no such reaction with the tri- 

 chlorpyromucic acid, in neither case had direct experiments in this 

 direction been made, and it was quite possible that the decomposition 

 in question had been overlooked. It was soon found, on trial, that tri- 

 brompyromucic acid was decomposed in analogous fashion, but that the 

 reaction was effected with much more difficulty, so that a temperature 

 materially above 100° was necessary in order to bring it about. When 

 heated to boiling with concentrated hydrobromic acid, carbonic dioxide 

 was evolved and a body melting at 90-91° was formed, which showed 

 a close resemblance to the monohalogenized bodies already known, 

 and which had the similar formula C 4 H 2 Br 2 2 . From trichlorpyro- 

 mucic acid the analogous body C4H 2 C1 2 2 , melting at 50-51°, could 

 be made without difficulty. In studying the behavior of other substi- 

 tuted pyromucic acids under the same conditions, it was found that 

 the /38-dibrompyromucic acid could also be made to undergo the same 

 decomposition, although but a comparatively small yield of a body 

 C 4 H 3 Br0 2 melting at 58° could thus be obtained. This mode of 

 decomposition was, therefore, not confined to those acids which con- 

 tained halogen at the same time in the y and 8 positions. By follow- 

 ing an entirely different method it was found that the /38-dibrompyro- 

 mucic acid could be converted into an isomeric body, C 4 H 3 Br0 2 , which 

 melted at 77°, and was identical with that which had already been 

 discovered by Hill and Sanger. The /38-dibrom pyromucic acid was 



