204 PROCEEDINGS OF THE AMERICAN ACADEMY 



From the structure of the j3y-dibrompyromucic acid, which has al- 

 ready been determined by Hill and Sanger,* it is evident that a sul- 

 phonic acid formed from it must of necessity contain the sulpho-group 

 in the 8 position. It therefore seemed to us of interest to prepare 

 from this /3y-dibrom-S-sulphopyromucic acid, by the elimination of the 

 bromine, the corresponding sulphopyromucic acid. Should this acid 

 prove to be identical with that made directly from pyromucic acid by 

 means of sulphuric acid, the 8 position of the sulpho-group in the latter 

 acid would be established with precision. A strongly ammoniacal so- 

 lution of baric /3y-dibrom-S-sulphopyromucate was warmed for some 

 time with an excess of zinc-dust. After reduction had taken place the 

 filtered solution was boiled with an excess of baric hydrate until the 

 ammonia had been expelled, and the excess of baric hydrate then re- 

 moved with carbonic dioxide. The concentrated solution deposited on 

 cooling hemispherical aggregations of colorless crystals, which upon 

 investigation proved to be identical in composition with the baric sul- 

 phopyromucate already described, and to have also the same solubility 

 in cold water. 



0.6194 grm. of the air-dried salt lost, at 160°, 0.1111 grm. H 2 0, and 

 gave 0.3614 grm. BaS0 4 . 



Calculated for 

 Ba(y I 2 SO„ . 4 H 2 0. Found. 



H 2 18.02 17.94 



Ba 34.34 34.30 



I. 12.9988 grm. of the solution saturated at 21° gave 0.3169 grm. 

 BaS0 4 . 

 II. 13.0993 grm. of the solution saturated at 21° gave 0.3181 grm. 

 BaS0 4 . 



The aqueous solution saturated at 21°, therefore, contained the fol- 

 lowing percentages of the anhydrous salt : — 



i. ii. 



3.42 3.41 



It will be seen that these results prove the identity of this salt with 

 that made directly from pyromucic acid. 



Action of Bromine. 



Bromine in aqueous solution readily oxidizes /3/-dibroni-8-sulphopy- 

 romucic acid or its salts. If a slight excess of bromine is added to an 



* These Proceedings, xxi. 181. 



