242 Royal Society .-— 



the oxide of the phosphorus-base 



C 6 H 15 PO=(C 2 H 5 ) 3 PO*. 



I have since confirmed this formula by actual analysis. 



The difficulties which in our former experiments opposed the 

 preparation of this compound in the pure state, arose entirely from 

 the comparatively small quantity of material with which we had to 

 work. Nothing is easier than to obtain the oxide in a state of 

 purity, provided the available quantity of material is sufficient for 

 distillation. In the course of a number of preparations of triethyl- 

 phosphine for new experiments, a considerable quantity of the 

 oxide had accumulated in the residues left after distilling the zinc- 

 chloride-compound with potash. On subjecting these residues to 

 distillation in a copper retort, a considerable quantity of the oxide 

 passed over with the aqueous vapours, and a further quantity was 

 obtained, as a tolerably anhydrous but strongly coloured liquid, by 

 dry distillation of the solid cake of salts which remained after all the 

 water had passed over. The watery distillate was evaporated on the 

 water-bath as far as practicable, with or without addition of hydro- 

 chloric acid ; and the concentrated solution was mixed with solid 

 hydrate of potassium, which immediately separated the oxide in the 

 form of an oily layer floating on the surface of the potash. The 

 united products were then left in contact with solid potash for 

 twenty-four hours and again distilled. The first portion of the 

 distillate still contained traces of water and a thin superficial layer 

 of triethylphosphine. As soon as the distillate solidified, the 

 receiver was charged, and the remaining portion — about nine-tenths 

 — collected separately as the pure product. To prevent absorption 

 of water, the quantity required for analysis was taken during the 

 distillation. 



With reference to the properties of oxide of triethylphosphine, I 

 may add the following statements to the description formerly givenf. 

 This substance crystallizes in beautiful needles, which,ifan appreciable 

 quantity of the fused compound be allowed to cool slowly, frequently 

 acquire the length of several inches. I have been unable to obtain 

 well-formed crystals ; as yet I have not found a solvent from which 

 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- 

 * II = 1 ; = 16 ; C = 12, &c. t Phil. Trans. 1357, p. 575. 



