206 PROCEEDINGS OF THE AMERICAN ACADEMY 



idly on exposure to the air. The melting point to the effloresced 

 substance was 150-151°, and the percentage of bromine it contained 

 showed that it was a dibromdinitrofurfuran. 



0.2008 grin, of the substance gave 0.2396 grm. AgBr. 



Calculated for 



U 4 Br 2 (N0 2 ) 2 0. Found. 



Br 50.63 50.79 



The clear crystals deposited from benzol evidently contained benzol 

 of crystallization. They effloresced so rapidly, however, that the exact 

 determination of the combined benzol was somewhat difficult. 



0.2611 grm. of the substance rapidly pressed and weighed lost, on 

 standing exposed to the air until the weight was constant, 

 0.0486 grm. benzol. 



Calculated for 

 C 4 Br 2 (N0 2 ) 2 . C 6 II . Found. 



C 6 H 6 19.80 18.61 



Considering the difficulty of such determinations, this result leaves 

 no doubt that this dibromdinitrofurfuran crystallizes with one molecule 

 of benzol. The mode of formation of this substance leaves no possible 

 doubt that it is the aa-dinitro-yS/3-dibromfurfuran. 



/3-Sulpho-S-Brompyromucic Acid. 



The three sulphonic acids thus far described contain the sulpho- 

 group in the 8 position, and, in the two cases where the formation of 

 isomeric products is theoretically possible, we have hitherto been un- 

 able to prove that any isomeric sulphonic acids are in reality formed. 

 For the preparation of such isomeric products it was, therefore, evi- 

 dently necessary to start with the 8-hydrogen atom otherwise replaced, 

 and the 8-brompyromucic acid formed the most convenient material. 

 We found no difficulty in preparing in this way a sulphonic acid, which 

 we have called the /3-sulpho-S-brompyromucic acid, and from it the 

 /3-sulphopyromucic acid itself may be made. Since the brominated 

 acid was of necessity first prepared, and we were able to investigate 

 it more fully, it may be more conveniently first described. 



S-brompyromucic acid dissolves in fuming sulphuric acid without 

 essential decomposition, and after the lapse of some time the formation 

 of the sulphonic acid appears to be complete. On neutralizing the 

 diluted solution with baric carbonate, a barium salt is obtained which 

 is sparingly soluble even in hot water, and which usually persistently 



