655 



dibromide of ethylene. These experiments, some of which have 

 been laid already before the Royal Society, whilst others are still in- 

 complete, have furnished many additional illustrations of the group 

 of polyammonias ; but most of these reactions are complicated, and 

 the compounds produced are far from always presenting the salient 

 characters which I could have desired. In fact, it was not until I 

 pursued the inquiry into the phosphorus-series, and relying on the 

 promptness and precision with which these substances act, examined 

 the deportment of dibromide of ethylene with triethylphosphine, that 

 the experiments were attended by the desired success. 



The new diphosphonium-compounds which form the subject of 

 this note are remarkable for their well-defined characters, and for 

 their stability. They may be heated to 250 C. without undergoing 

 the slightest change. Even the dioxide, which is readily liberated 

 by the action of oxide of silver upon either the bromide or the iodide, 

 is a very stable compound. The solution of this substance, which 

 obviously corresponds to 2 molecules of water, 



2 molecules Molecule of the diphosphonium- 



of water. compound. 



is a powerfully alkaline liquid, attracting with great avidity the car- 

 bonic acid of the atmosphere, and precipitating the metallic oxides 

 like potassa. The solution may be evaporated without change to a 

 syrup-like liquid, and it is only at a very high temperature that 

 decomposition actually takes places. At one time I had hoped to 

 see this body splitting under the influence of heat into the ethylene- 

 alcohol (glycol) and triethylphosphine, but the transformation ensues 

 in another form, only traces of phosphorus-base being liberated, 

 while the principal product is the dioxide of triethylphosphine, which, 

 in the latter stages of the distillation, coats the neck of the retort 

 with a network of beautiful needles ; a small quantity of gas (hydride 

 of ethyl?) being simultaneously evolved. 

 The reaction is probably 



[(C 4 H 5 ) 6 (C 4 H 4 )" PJ" | ^ c H 6 +2[(C 4 H 5 ) 3 P0 2 ] ; 



this equation, however, is not experimentally established. 



The molecule of the diphosphonium-bromide contains the elements 



