258 



The brominated derivatives of ethylene have been chiefly examined 

 by Regnault and by Cahours, and more recently by Wurtz and by 

 Sa witch. 



The following terms have been obtained : 



Dibromide of Ethylene. 

 C 2 H 4 Br a . 



Dibromide of Monobrominated 

 Ethylene. 



Monobrominated Ethylene. 

 C 2 H 3 Br. 



Dibrominated Ethylene. 

 C 2 H 2 Br 2 . 



C 2 (H 3 Br)Br 2 . 



Tribrominated Ethylene. 



C HBr,. 



Dibromide of Dibrominated Ethylene. 

 C 2 (H 2 Br 2 )Br 2 . 



Dibromide of Tribrominated Ethylene. 

 C 2 (HBr 3 )Br a . 



It thus appears that the whole series has been obtained with the 

 exception of the tetrabrominated ethylene and its corresponding dibro" 

 mide, the former of which would be the bromide of carbon obtained 

 by Lowig in the reactions above indicated. Of the brominated deri- 

 vatives of ethylene, dibromide of ethylene, monobrominated ethylene 

 (bromide of vinyl) and dibromide of monobrominated ethylene, have 

 as yet been best investigated. In re-examining these substances, in 

 transforming dibromide of ethylene by the action of an alcoholic 

 solution of potash into monobrominated ethylene, and the latter by 

 treatment with bromine into the corresponding dibromide, I had an 

 opportunity of tracing step by step the observations of my pre- 

 decessors. 



Dibrominated Ethylene. 



The action of an alcoholic solution of potash upon the dibromide 

 of monobrominated ethylene yields, together with secondary products, 

 a comparatively small quantity of the oily compound C 2 H 2 Br 2 , which 

 is still further diminished by the extraordinary property exhibited by 

 this substance of undergoing a molecular transformation similar to 

 that of dichlorinated ethylene as observed by Regnault*, and of 

 monobrominated ethylene more recently examined by Dr. Hofmann^j*. 

 Dibrominated ethylene having been lately the subject of a minute 

 investigation by M. SawitchJ, I have not entered upon a more 



* Annales de Chimie et de Physique, [2] vol. Ixix. p. 151. 

 t Quarterly Journal of the Chemical Society, xiii. 68. 

 t Bulletin de la Societe Chimique de Paris, 1860. 



