Dr. Hofmann on Oxide of Triethylphosphine. 243 



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* 1 50 grm. 



Volume of vapour 49' 1 cub. cent. 



Temperature (corrected) 26 6' 6 



Barometer at 0° 07670 metre. 



Additional mercury column at 0° 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 =i|^= 67, 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 

 the very high boiling-point of the resulting compound, in consequence 

 of which the vapour of the latter can exert but a very slight tension 

 at the common temperature, I am induced to think that the phos- 

 phorus-base may be used in many cases for the volumetric estimation 

 of oxygen. When a paper ball soaked in triethylphosphine is passed 

 up in a portion of air confined over mercury, the mercury immedi- 

 ately begins to rise, and continues to do so for about two hours, after 

 which the volume becomes constant, the diminution corresponding 

 very nearly to the proportion of oxygen in the air. To obtain very 

 exact results, however, it would be probably necessary in every case 

 to remove the residual vapour of triethylphosphine by means of a 

 ball saturated with sulphuric acid. 



Oxide of triethylphosphine exhibits in general but a small tendency 

 to unite with other bodies. Nevertheless it forms crystalline com- 

 pounds with iodide and bromide of zinc. I have examined more 

 particularly the iodine-compound. 



Oxide of Triethylphosphine and Iodide of Zinc. — On mixing the 

 solutions of the two bodies, the compound separates, either as a 

 crystalline precipitate or in oily drops which soon solidify with 

 crystalline structure. It is easily purified by recrystallization from 

 alcohol, when it is deposited in often well-formed monoclinic crystals 

 containing ^ H _ p0 ^ ZnJ = ^ H ^ pQj ^ 



It is remarkable that this compound formed in presence of a large 

 excess of hyclriodic and even of hydrochloric acid. 



Oxide of Triethylphosphine and Dichloride of Platinum. — No pre- 

 cipitate is formed on mixing the aqueous solutions of the two com- 

 * H. 2 = 2 vols, vapour. 



