176 PROCEEDINGS OF THE AMERICAN ACADEMY 



0.2720 grm. gave 0.3600 grm. AgBr. 



Calculated for C^HBrjOj . CjHg. Found. 



Br 55.94 56.32 



Action of Br mi e. 



Limpricht and Delbriick studied in delr i1 the action of bromine and 

 water upon mucobromic acid, but they made no experiments witli dry 

 bromine. It therefore seemed advisable to investigate the action of 

 dry bromine ; since the reactions in this case would naturally be less 

 complicated tlian with aqueous bromine, and on that account might 

 prove to be of more service in determining the constitution of muco- 

 bromic acid. Li my first experiments I employed equal molecules 

 of bromine and mucobromic acid, but soon found that one molecule 

 of bromine sufficed for tlie complete decomposition of nearly two 

 molecules of mucobromic acid, although tlie products of the reaction 

 were esseutiiilly the same whether the bromine was used in excess or 

 not. 



At 100°, vejry little action was noticeable; at 120-130°, the action 

 was marked, but so slow tliat the temperature was raised to 140°. 

 Here the I'eaction ran rapidly, and after two hours the bromine had 

 disappeared. On cooling, the tubes were filled with long, prismatic 

 crystals, which were permeated with a nearly colorless oil. On open- 

 ing the tubes, hydrobromic acid gas escaped in abund:mce, and with it 

 could be detected a comparatively small amount of cai'bouic dioxide. 

 The partially solidified product of the reaction was treated with small 

 quantities of cold water. The greater part of the prismatic crystals 

 were in tliis way carried into solution ; while the oil, in which a small 

 quantity of crystals were yet to be seen, was left undissolved. This 

 aqueous solution, upon evaporation, left a white, crystalline acid, very 

 soluble in water, which for purification was converted into tlie barium 

 salt. Before neutralizing the aqueous solution with baric carbonate, 

 I found it best to evaporate to dryness, and take up a second time 

 with a little cold water, in order to remove the small quantity of uude- 

 composed mucobromic acid which often was present. The barium 

 salt was precipitated several times from aqueous solution by alcohol, 

 and finally crystallized from water by evaporation. Thus purified, it 

 formed brilliant, transparent, rhombic plates, which lost water in 

 desiccator slowly, but which I was unable to dehydrate perfectly by 

 heat, either at ordinary pressures or in vacuo, without causing partial 

 decomposition. The analysis of the air-dried salt gave percentages 



