288 



stalline substance being immediately precipitated. If the reaction be 

 allowed to go on in the presence of a large volume of anhydrous 

 ether, the deposition of the crystalline body is considerably retarded, 

 unless the mixture, in an appropriate apparatus, be exposed to the 

 temperature of boiling water. After a short digestion, on distilling 

 off the ether and the excess of bibromide, a crystalline cake is left in 

 the retort, consisting of several bromides, the nature and the relative 

 proportions of which appear in a great measure to depend upon the 

 rapidity of the reaction. I have found it most convenient to work 

 with ethereal solutions at the common temperature. 



The determination of the bromine in the crystalline body revealed 

 at once the compound character of this substance, for it steadily 

 diminished by dissolving the bromide in absolute alcohol, and repre- 

 cipitating it partially by ether. By repeating this process four or 

 five times, a body of constant composition was obtained. 



The compound thus prepared is a crystalline mass, without odour, 

 extremely soluble in water, and even in absolute alcohol, but inso- 

 luble in anhydrous ether. It exhibited a rather unexpected compo- 

 sition, for on analysis it was found to contain 



C 16 H 19 PBr 2 , 



and consequently to have been formed by the simple union of 1 equi- 

 valent of triethylphosphine and 1 equivalent of bibromide of ethy- 



lene, 



C 12 H 15 P + C 4 H 4 Br 2 = C 16 H 19 PBi V 



The bromine in this compound exists in two perfectly different 

 forms ; addition of nitrate of silver precipitated only one-half of this 

 element as bromide of silver, while even by protracted ebullition the 

 second half remained untouched. The result changed, however, on 

 digestion with freshly precipitated oxide of silver, when the whole of 

 the bromine separated at once in the form of bromide of silver. 



On adding to the solution of the bromide an excess of nitrate of 

 silver, filtering off the bromide, and removing the excess of silver by 

 hydrochloric acid, a corresponding chloride was obtained, from which 

 bichloride of platinum precipitated a beautiful orange-yellow pla- 

 tinum-salt. In a moderately diluted solution which had been pre- 

 viously gently heated, no immediate precipitate was produced ; but 

 on cooling, the same salt was deposited in magnificent needles, which 



