OF ARTS AND SCIENCES. 



183 



tetrabromide whose formula is given above two isomeric dibrom- 

 pyromucic acids can ia any case be formed ; but if the second 

 formula for pyromucic acid be adopted, these would necessarily have 

 the structure, 



both of which would yield on oxidation monobromfumaric or mono- 

 brommaleic acid. On the other hand, the adoption of either the first 

 or the third formula for pyromucic acid would give for the resulting 

 dibrompyromucic acids the forms, 



or. 



BrC=C-COOH 



\ 

 O 



/ 

 BrC = CH 



BrC - C - COOH 



A/ 



BrC CH 



and 



and 



In either case, the oxidation products which we have observed would 

 find in these formulae a natural explanation. 



While either of these two formuhe will explain the facts which we 

 have observed, it seems to us that there can be no doubt tliat prefer- 

 ence should be given to the first. Aside from the difficulty of explain- 

 ing by means of the third formula the formation of the pyromucic 

 tetrabromide, and the re-establishment of the carbon ties by the action 

 of caustic alkalies, the formation of Heintzlemann's dehydromucic acid 

 from raucic acid, which certainly is a dicarboxyfurfuran, would neces- 

 sitate the assumption of a mode of dehydration in whose support, so 

 far as we are aware, no analogous cases can be advanced. On the 

 other hand, the ready formation of the lactones, as sliown by the 

 brilliant researches of Fittig, renders the formation of a stable oxide 

 by the elimination of water involving bydroxyl groups attached to 

 the first and fourth carbon atoms a matter in every way probable. 

 We cannot deny that tiie adoption of the first formula renders the 



