605 



this substance could be crystallized. It is soluble in all proportions, 

 both in water and alcohol, and separates from these solvents on 

 evaporation in the liquid condition, solidifying only after every 

 trace of water or alcohol is expelled. Addition of ether to the 

 alcoholic solution precipitates this body likewise as a liquid. The 

 fusing- point of oxide of triethylphosphine is 44 ; the point of 

 solidification at the same temperature. It boils at 240 (corr.). 



As no determination of the vapour-density of any member of the 

 group of compounds to which oxide of triethylphosphine belongs 

 has yet been made, it appeared to me of some interest to perform 

 this experiment with the oxide in question. As the quantity of 

 material at my disposal was scarcely sufficient for the determination 

 by Dumas' s method, and Gay-Lussac's was inapplicable on account 

 of the high boiling-point of the compound, I adopted a modifica- 

 tion of the latter, consisting essentially in generating, the vapour 

 in the closed arm of a U-shaped tube immersed in a copper vessel 

 containing heated paraffin, and calculating its volume from the 

 weight of the mercury driven out of the other arm. Since I intend 

 to publish a full description of this method, which promises to be 

 very useful in certain cases, I shall here content myself with stating 

 the results obtained in one of the experiments. 



Substance 0-150 grm. 



Volume of vapour 49' 1 cub. cent. 



Temperature (corrected) 266'6 



Barometer at 07670 metre. 



Additional mercury column at 0'1056 



These numbers prove the vapour-density of oxide of triethyl- 

 phosphine to be 66*30, referred to hydrogen as unity, or 4'60 re- 

 ferred to atmospheric air. Assuming that the molecule of oxide of 

 triethylphosphine corresponds to 2 volumes of vapour*, the spec, 

 grav. of its vapour =-Mp.= 6 7, when referred to hydrogen, and 4'63 

 when referred to air. Hence we may conclude that in oxide of 

 triethylphosphine the elements are condensed in the same manner as 

 in the majority of thoroughly investigated organic compounds. 



From the facility with which triethylphosphine is converted into 

 the oxide by exposure to the air, even at ordinary temperatures, and 



* H^O-2 vols. vapour. 



