BENZYL PHOSPHINES AND THEIR DERIVATIVES. 555 



series to which he extended his investigations was that of benzyl, and in the paper 

 published in the Berichte, to which we have already referred, he describes the 

 preparation and properties of dibenzyl phosphine. He isolated it from the product of 

 the sealed tube reaction (occurring between benzyl chloride, phosphonium iodide, and 

 oxide of zinc), but it is not quite clear from the original memoir whether he obtained it 

 from the residue left on distilling the primary phosphine in a current of steam from the 

 product of the reaction, or the residue left on distilling the crude primary phosphine 

 itself. He states that a crystalline substance remains after distilling off the primary 

 phosphine, which solidifies, especially (zumal) in contact with solid potash, and that after 

 pressing it between linen, dissolving in alcohol, and decolorising the solution with 

 charcoal, crystals are obtained, which after a single recrystallisation from alcohol are 

 perfectly pure. 



The crystals melted at 205°, and their analysis gave the following numbers : — 



Obtained. 





1. 



II. 



III. 



,o '"' ii,ku "" ^ 



Carbon, . 



7S-75 



78-37 





78-50 



Hydrogen, 



6-99 



677 





701 



Phosphorus, . 







136 



1449 



He says : — " With the entrance of the second group the basic properties, which in 

 benzyl phosphine appear in a perfectly definite manner, have entirely disappeared. 

 Dibenzyl phosphine dissolves in no acid, neither have I succeeded in obtaining its 

 platinum salt. The aromatic secondary phosphine thus distinguishes itself very materially 

 from the secondary phosphines of the ethyl and methyl series." 



In a paper read before this Society, one of us, in conjunction with W. Wheeler, 

 described further investigations on this body, and we showed that it forms a series of 

 compounds of a somewhat remarkable nature for a secondary phosphine. We isolated it 

 as follows : — After submitting the contents of the sealed tubes to the action of steam 

 and water (to drive off the primary phosphine), the residue, consisting of a brownish 

 viscous mass, was boiled with aqueous potash for some time, and the viscous insoluble 

 mass which remained was then extracted with hot alcohol. The solution on cooling- 

 deposited colourless needle-shaped crystals strongly impregnated with oily matter, and 

 these by repeated recrystallisation from spirit were obtained pure. 



The remarkable nature of this substance, on the assumption that it is in reality a 

 secondary phosphine, coupled with some other facts which attracted our attention, 

 gradually led us to suspect that it was not dibenzyl phosphine at all, but the oxide of 

 tribenzyl 'phosphine. Accordingly, the investigation was reopened with Mr K. F. Blake, 

 and its course has been as follows : — 



1. On carefully recrystallising the substance from alcohol, its corrected melting- 

 point was found to be 215°-215°*5 C, while that of two specimens of oxide of tribenzyl 

 phosphine (prepared by two different methods) was found to be the same. 



