259 



close examination of this body, but have at once, by the renewed 

 action of bromine, converted it into the 



Dibromide of Dibrominated Ethylene. 



Bromine attacks the dibrominated ethylene with the greatest 

 energy; heat is evolved, and the bromine disappears. When the 

 bromine was no longer fixed, the orange-yellow liquid thus produced 

 was treated with a weak solution of potash, washed with water, and 

 ultimately distilled with precaution. It boils at about 200 C., but not 

 without partial decomposition ; white fumes containing hydrobromic 

 acid being given off during ebullition, which powerfully and persist- 

 ently attack the eyes. 



The bromine-compound is insoluble in water, but dissolves readily 

 in alcohol and in ether. When exposed to a freezing mixture, it 

 solidifies to a white crystalline mass. It was found impossible to 

 purify this substance for analysis by distillation ; a current of per- 

 fectly dry carbonic acid gas was therefore passed through the liquid 

 heated in a water bath to about 75. After a time it assumed a 

 lighter col our, and no longer gave off hydrobromic acid ; it was then 

 found to contain 



C 2 H 2 Br,. 



Tribrominated Ethylene. 



The dibromide previously described is powerfully acted upon by an 

 alcoholic solution of potash, 



C 2 H 2 Br 4 +KHO=C 2 HBr 3 + KBr+H 2 O. 



Addition of water to the alcoholic solution precipitates the tribro- 

 minated ethylene as an oily substance boiling at 130C., which by 

 digestion with chloride of calcium and subsequent careful distillation, 

 may be obtained sufficiently pure for analysis. 



The results obtained in the analysis of this compound prove it to 

 be represented by the formula 



C 2 HBr 3 . 



Tribrominated ethylene, like the other substitution-products of 

 ethylene, is apt to furnish an isomeric solid, readily soluble in 

 alcohol and in ether, from which it crystallizes in colourless plates. 

 On slowly evaporating a solution of the oily modification in alcohol or 

 ether, the crystalline solid is likewise obtained. 



