186 PROCEEDINGS OF THE AMERICAN ACADEMY 



the filtered solution baric dibrommaleate in characteristic form. For 

 analysis, the salt was recrystallized from water, and dried by exposure 

 to the air. 



. 0.4709 grm. of this salt gave 0.2516 grm. BaSO^. 



Calculated for BaC4Brj04.2H,0. Found. 



Ba 30.78 31.41 



Since the percentage of barium was found to be too high, for further 

 identification the acid was set free, and converted into the anhydride 

 by sublimation. This crystallized in the characteristic flattened 

 needles, which melted at 114°. The quantity of dibrommaleic acid 

 formed in the ordinary preparation of mucobromic acid is very incon- 

 siderable, and amounted in one case to about one per cent of the 

 pyromucic acid emjjloyed. The quantity must, however, of necessity 

 be very variable. 



The oxidation of mucobromic acid by means of argentic oxide was 

 investigated by Schmelz and Beilstein. They gave to the chief prod- 

 uct of the reaction the formula, AgjC^HgBrgO. ; but it is evident 

 from an inspection of their analyses that they had in their hands the 

 silver salt of dibrommaleic acid in a nearly pure condition. 



With this close agreement between the observed and calculated per- 

 centages, I did not consider it worth while to analyze, myself, this 

 silver salt. Still it was evidently necessary to prepare from it the 

 barium salt in order to compare this with the product I had already 

 studied. 



Since argentic bromide is readily formed when tlie silver salt of 

 mucobromic acid is heated with water, I added at once an excess of 

 argentic oxide to a warm solution of mucobromic acid, and heated it 

 quickly to the boiling point. The oxidation seemed to be more neatly 

 accomplished in this way than by the gradual addition of the argentic 

 oxide, although even then there was formed a considerable quantity of 

 argentic broniide. After the action had ceased, the whole was acidified 

 with hydrochloric acid, and the filtered solution shaken out witli ether. 

 The acid left upon evaporation of the ether was then taken up with 

 water, neutralized with baric carbonate, and the barium salt purified as 



