472 
DE. A. ^Y. HOFMAXX OX THE PHOSPHOEUS-BASES. 
the compound 
dibromide of ethylene exhibits a deportment 'which might have been expected from 
bromide of bromethyl, with which it is isomeric. It was of some interest to examine, 
experimentally, the beha’vdour of triethylphosphine ■with monobrcminatecl bromide of 
ethyl. This substance had never been prepared. I have obtained it, together -with the 
dibrominated bromide of ethyl (C 2 H-, Br 2 ) Br, by submitting bromide of ethyl to the 
action of dry bromine under pressure at a temperatm’e of 180° C. Brominated bromide 
of ethyl is a heavy aromatic oil, boiling at 110° C., and consequently difFeiing altogether 
from dibromide of ethylene, Avhich boils at 130° C., and with which it is isomeric. The 
brominated bromide attacks the phosphorus-base much more slowly than the dibromide ; 
the final result, however, is exactly the same, the bromide of the bromethylated mono- 
phosphonium and the dibromide of the ethylene-diphosphonium being produced. The 
former of these salts is obtained in comparatively small quantity, and I was therefore 
unable to identify the compound in question with the bromethylated bromide foiTued by 
means of the ethylene-compound, otherwise than by the characteristic reaction ■with silver- 
salts, mentioned in an earlier paragraph of this paper. The diphosphoniuni-compound. 
on the other hand, is easily produced from brominated bromide of ethyl in sufficiently 
large quantity. I had no difficulty in establishing the absolute identity of this com- 
pound with the product obtained from dibromide of ethylene, by a careful comparison 
of the chemical and physical properties of the substances, and moreover by the analysis 
of a di-iodide and a platinum-salt prepared by means of the bromide-of-ethyl-deriva- 
tive. These analyses are given among the analytical details establishing the composition 
of these salts. 
Bihydrate . — The free base is easily obtained by the action of oxide of silver on the 
dibromide, or better on the di-iodide, which latter is, of all the diphosphonium-com- 
pounds of this class, the easiest to obtain in the pure state. If the alcoholic solution of 
the crude dibromide be used in this experiment, the first portions of oxide of silver 
added to the liquid are completely dissolved, and the solution, which has already become 
alkaline, deposits a white crystallized double compound of the dibroniidc with bromide 
of silver, which, however, is completely decomposed by further addition of oxide of silver 
and dilution with water. In this manner there is produced an extremely caustic, nearly 
odourless liquid, having a strongly alkaline taste, and exhibiting the same bitterness 
which is so often observed in the analogous bodies of the nitrogen-series. In other 
respects, the base exhibits the properties which characterize the hydrates of tetrethyl- 
phosphonium* and tetrethylammonium f. The solution, when evaporated in an open 
vessel, rapidly absorbs carbonic acid, and ultimately yields a semi-crystalline mixture 
of dihydrate and carbonate. When evaporated in vacuo over sulphuric acid, tlie caustic 
solution gradually dries up to a syrupy, extremely deliquescent mass, Avhich exhibits no 
traces of crystallization. On mixing the highly concentrated solution of the diliydrate 
* Philosopliical Trausactions, 1857, Part II. p. 583. t Ibid. 1851, Part II. p. 357. 
