202 PROCEEDINGS OF THE AMERICAN ACADEMY 



In one instance the salt precipitated from alcoholic solution by the 

 addition of ether was found to contain but a single molecule of water. 

 1.0639 grm. of air-dried salt lost over H2S0^ in vacuo 0.0458 grm. 



Calculated for BaCCaBrOjlj.HjO. Found. 



H2O 3.99 ' 4.30 



The salt usually crystallized, on the slow evaporation of its aqueous 

 solution, in small, oblique prisms ; but it sometimes separated, on long 

 standing, in more compact, clustered, rhombic plates. When dry, it is 

 decomposed quite rapidly at 50°, and deflagrates at about 125°. In 

 aqueous solution it is recomposed on boiling, with the precipitation of 

 baric carbonate and the evolution of carbonic dioxide and bromacety- 

 len. From solutions containing an excess of the acid, a somewhat 

 more stable salt separates in fine, felted needles, less soluble in water 

 than the neutral salt. This would seem to be an acid salt, corre- 

 sponding to the acid potassium salt of dibromacrylic acid ; but we 

 could obtain no satisfactory analytical results. 



When argentic nitrate is added to a solution of the barium salt, or of 

 the free acid, a white, amorphous silver salt is precipitated, and at 

 the same time if the solution is concentrated the evolution of carbonic 

 dioxide is noticed. The precipitate turns yellow on washing, and is 

 evidently still further decomposed on drying. When gently warmed 

 with water, it is slowly decomposed ; but, when suddenly heated nearly 

 to 100°, it explodes violently, with the separation of large quantities 

 of carbon. In a dry state it explodes when heated to about 75°. In 

 dilute nitric acid it dissolves at first; but the solution soon grows 

 turbid, smells strongly of bromacetylen, and argentic bromide is precipi- 

 tated. One could hardly expect trustworthy results from the analysis 

 of so unstable a substance. One silver determination, however, showed 

 that it must be considered a derivative of bromacetylen, rather than 

 of brompropiolic acid. 



0.2313 grm. of substance, dried over HjSO^ in vacuo, gave 0.1975 

 grm. AgBr. 



Calculated for AgCsBrOj ; for AgCjBr. Found. 



Ag 42.19 50.94 49.05 



Although the barium salt had given unsatisfactory results on analy- 

 sis, we made from it the acid, and hoped then to be able to effect its 

 purification. We therefore precipitated the barium from a cold, 

 aqueous solution, with a slight excess of sulphuric acid, and extracted 

 the acid from the filtered solution with ether. We obtained in this 



