OP ARTS AND SCIENCES. 199 



The filtered solution was boiled with a slight excess of baric hy- 

 drate until all the ammonia was expelled and the zinc precipitated. 

 The solution was then freed from the excess of baric hydrate by 

 means of carbonic dioxide, and concentrated on the water-bath. On 

 cooling, the solution deposited globular aggregations of colorless crys- 

 tals, which appeared to be identical with those of baric S-sulphopyro- 

 mucate. The identity was fully established by analyses of the salt, 

 and by determinations of its solubility in water. 



I. 1.5700 grm. of the air-dried salt lost, at 165°, 0.2803 grm. H 2 0. 

 II. 0.7309 grm. of the air-dried salt gave 0.4295 grm. BaS0 4 . 



Calculated for Found. 



BaC 5 H 2 S0 r> . 4 H 2 0. I. II. 



H 2 18.02 17.85 



Ba 34.34 34.55 



0.4947 grm. of the salt dried at 165° gave 0.3505 grm. BaS0 4 . 



Calculated for 

 BaC 6 H 2 S0 6 . Found. 



Ba 41.90 41.67 



I. 12.0595 grm. of the solution saturated at 21° gave 0.2985 grm. 

 BaS0 4 . 

 II. 12.1863 grm. of the solution saturated at 21° gave 0.2989 grm. 

 BaS0 4 . 



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

 lowing percentages of the anhydrous salt: — 



i. ii. 



3.47 3.44 



These results are sufficient to prove that the sulphonic acid formed 

 by the reduction of the /3-brom-S-sulphopyromucic acid is identical with 

 that obtained directly from pyromucic acid by the action of sulphuric 

 acid. 



Action of Bromine. 



Bromine in aqueous solution readily oxidizes /3-brom-S-sulphopyro- 

 mucic acid or its salts. Since the relative position of the bromine and 

 the sulpho-group had already been established, we thought it necessary 

 to do no more than identify the final product of the oxidation. Bro- 

 mine was added in slight excess to an aqueous solution of the barium 

 salt, and the reaction completed at a gentle heat. The strongly acid 

 solution was filtered from the baric sulphate which had been formed, 



