200 PROCEEDINGS OF THE AMERICAN ACADEMY 



aqueous solution gives, on the addition of plumbic acetate, an imme- 

 diate crystalline precipitate of plumbic dibromacrylate. 



0.3560 grm. gave, on ignition with H^SO^, 0.1628 grm. PbSO^. 



Calculated for PbCCsHBxjOj)!. Found. 



Pb 31.13 31.25 



So also if it is neutralized with baric carbonate, the solution gives, 

 on spontaneous evaporation, crystals of baric dibromacrylate, while in 

 solution remains a much more soluble salt, with all the characters of 

 baric brompropiolate. That this substance contains the brompropiolic 

 acid is shown by the evolution of carbonic dioxide and bromacetylen 

 when its aqueous evolution is boiled. 



Starting with this molecular compound melting at 104— 105°, we 

 made various attempts to isolate the brompropiolic acid and its salts in 

 a pure state. The barium salts of dibromacrylic and brompropiolic 

 acids showed such marked differences in their solubility in water or in 

 alcohol that we hoped through them to effect a complete separation of 

 the two acids. We found, however, that it was difficult to obtain in 

 this way a colorless salt of brompropiolic acid which appeared even 

 tolerably pure. "We therefore attempted to separate the two acids by 

 converting them into their ethyl-ethers and submitting these to frac- 

 tional distillation. We dissolved the molecular compound (m. pt. 

 104°) in absolute alcohol, added concentrated sulphuric acid, and 

 warmed. The ethers soon separated in part, and were precipitated 

 with water, washed with dilute sodic carbonate, and dried over fused 

 calcic chloride. These mixed ethers had an extremely sharp, pungent 

 odor, and their vapor attacked the eyes violently. On attempting to 

 separate the two by distillation, we found that a large portion of the 

 liquid was carbonized in each distillation, and that but one volatile 

 product could be isolated. This was a mobile liquid, of an agreeable 

 aromatic odor, which boiled between 209 and 215°, without any very 

 noticeable decomposition. The portion of this which boiled between 

 212-214° was analyzed, and found to be essentially the ethyl-ether 

 of dibromacrylic acid, although still impure. Since our chief object 

 was to isolate the ether of the brompropiolic acid, and this had evi- 

 dently been for the most part destroyed, the substance was not farther 

 examined. 



0.5235 grm. of substance gave, on combustion, 0.4675 grm. COg and 

 0.1250 grm. U.fi. 



