BENZYL PHOSPHINES AND THEIR DERIVATIVES. 559 



floats on the surface of the melted alkali. No violent action occurs, but on cooling the 

 mixture and treating it with water the greater portion dissolves, and acids then precipi- 

 tate a flocky crystalline substance, which is dibenzyl phosphinic acid." In corroboration 

 of this statement, the melting point of the acid and analyses of its lead and barium salts 

 were given, all in accordance with the required numbers. After we had satisfied 

 ourselves that Hofmann's dibenzyl phosphine was oxide of tribenzyl phosphine, and 

 nothing else, this reaction recurred to our minds as a further and very striking excuse 

 for the mistake which we (and Hofmann) had fallen into, and we thought it of im- 

 portance to verify the previous observation. This we have accordingly done, both with 

 Hofmann's dibenzyl phosphine and with a specimen of oxide of tribenzyl phosphine 

 prepared by a different process. 



The phenomena observed were exactly the same as those previously described, and 

 the melting point of the acid obtained after two recrystallisations from alcohol was found 

 to be 192° C. (corr.), which is the melting point of pure dibenzyl phosphinic acid. Our 

 previous observations are thus fully confirmed. 



The reaction in all probability occurs as follows : — 



(C 7 H 7 ) 3 PO + KHO = C 7 H 8 + (C 7 H 7 ) 2 KP0 2 . 



Investigation of the Product of the Sealed Tube Eeaction for the Secondary 



and Tertiary Phosphine. 



The occurrence of oxide of tribenzyl phosphine among the products of the sealed 

 tube reaction led us to suspect that the tertiary phosphine had been formed in the 

 first instance, but was subsequently oxidised by the air, as in isolating the oxide all 

 the operations had been performed in open vessels. Quite accidentally, our suspicions 

 received strong confirmation. 



In one of our later experiments, after the primary phosphine had been distilled 

 from the crude product of the reaction in a current of steam, the viscous mass remain- 

 ing was treated with an alcoholic solution of potash, instead of an aqueous solution as 

 we had used in our earlier experiments. 



After boiling for about four hours with alcoholic potash, in a flask fitted with an 

 upright condenser, the solution was filtered from oxide of zinc, &c, and on cooling 

 deposited feathery crystals like sal-ammoniac, and not at all like the needle-shaped 

 crystals of oxide of tribenzyl phosphine. The liquid was decanted from these crystals, 

 and to remove adhering potash they were washed with cold water, and were then 

 pressed between filter-paper to dry them. On unfolding the paper, the crystalline mass 

 grew very hot, and after repeated recrystallisation from alcohol (in an open vessel), the 

 resulting crystals were needle-shaped, and had a melting point of 21 5° '5 (corr.). 



The conclusions we drew from this result were that the tertiary phosphine is formed 

 in the reaction, and that it is a solid crystalline body which rapidly absorbs oxygen from 

 the air with disengagement of heat, and is eventually converted into its oxide. 



VOL. XXXV. PART II. (NO. 15). 4 Y 



