198 PROCEEDINGS OF THE AMERICAN ACADEMY 



One well-marked product of the decomposition of mucobromic acid 

 by cold baric hydrate had been shown to be baric dibromacrylate ; it 

 only remained to study the more soluble products of the reaction. In 

 continuing the investigation with Mr. O. R. Jackson, the filtrate from 

 the crystals of baric dibromacrylate was treated with carbonic dioxide 

 to remove the excess of baric hydrate, filtered from the baric carbon- 

 ate, and the filtrate evaporated at a gentle heat (40-50°). In the 

 course of this evaporation, a certain amount of baric dibromacrylate 

 crystallized out, which was removed from time to time. When the 

 liquid had been reduced to about one third its original volume, it was 

 precipitated by the addition of two volumes of alcohol. The bulky 

 crystalline precipitate thus thrown down proved upon qualitative ex- 

 amination to consist chiefly of baric formiate. When purified by 

 repeated precipitation from aqueous solution by alcohol and recrystal- 

 lization from water, it showed the characteristic form of baric formiate. 



0.3964 grm. substance gave, on ignition with H^SO^, 0.4054 grm. 

 BaSO,. 



Calculated for Ba (CHOjjj. Found. 



Ba 60.36 60.13 



The lead salt made from the barium salt crystallized in the charac- 

 teristic form of plumbic formiate, and gave on analysis the required 

 percentage of lead. 



0.4149 grm, of the salt gave, on ignition with HgSO^, 0.4221 grm. 

 PbSO,. 



Calculated for Pb (CHOj),. Found. 



Pb 69.69 69.50 



In the alcoholic filtrate from the baric formiate, we were able to find, 

 beside baric bromide, only a crystallizable barium salt, well marked by 

 its qualitative reactions, but so unstable that we were not able to effect 

 its purification. The behavior of this salt, and the analyses which we 

 made of it in an impure state, led us to the conclusion that it was 

 the barium salt of bronipropiolic acid, formed by subtraction of hydro- 

 bromic acid from the dibromacrylic ; and this view was subsequently 

 proved to be correct by a study of the addition products which the 

 corresponding acid formed with the halogens and the haloid acids. 



Since all our attempts to isolate a pure salt from a solution con- 

 taining baric bromide had proved unsuccessful, we attempted to take 

 advantage of a remarkably stable molecular compound which the 

 corresponding acid forms with dibromacrylic acid. This compound 



