BENZYL PHOSPHINES AND THEIR DERIVATIVES. 565 



anhydride, when a yellowish liquid remained, which on cooling became semicrystalline. 

 When perfectly dry it weighed 6 4 '5 grms. It was examined as follows : — 



(1) On adding ether, a good deal remained undissolved (probably "insoluble crystalline 

 body"). 



(2) Six grms. of the crude product were mixed with 6 grms. of crystallised iodide of 

 benzyl. On agitation the mixture grew excessively hot. When cold the mass was 

 extracted with ether (to remove the excess of iodide of benzyl and any other impurities), 

 then boiled with alcohol, and the solution allowed to crystallise. The resulting crystal- 

 line mass of crude iodide of tetrabenzyl phosphonium weighed when dry 5 '5 grms., 

 which with the quantity of substance operated upon correspond with 53 per cent, of 

 tribenzyl phosphine. 



The crude iodide was purified by recrystallising it four times from alcohol. 



Analysis. 



0-3956 gave 01758 Agl = 0-095006 I = 24-01 per cent. 



Obtained. Calculated for (C 7 H 7 ) 4 PI 



Iodine, . . 24-01 2432 



To identify the iodide with absolute precision some of it was converted into acid 



sulphate (by boiling with diluted sulphuric acid), and an analysis made of the purified 



product. 



Analysis. 



05726 grms. gave 02679 BaS0 4 = 0*1103793 S0 4 = 19-27 per cent. 



Found. Calculated for (C 7 H 7 ) 4 P.HS0 4 



S0 4 . . . 19-27 1951 



(3) 5 '67 5 5 grms. were exposed to the air in a platinum dish, but no heat was de- 

 veloped. Weak baryta solution was then added, and the mixture evaporated to dryness : 

 redissolved several times with fresh quantities of water and evaporated to dryness, in 

 order to ensure complete oxidation. The residue was then boiled with water, the solution 

 filtered and mixed with hydrochloric acid, but no definite precipitate of dibenzyl phos- 

 phinic acid could be obtained. 



However, on boiling the residue with caustic potash, then extracting with water and 

 acidulating the solution with hydrochloric acid, a very bulky precipitate of dibenzyl 

 phosphinic acid was obtained, which weighed when washed and dried 1"1300 grms.* The 

 insoluble residue from the potash treatment was oily. It was extracted with ether several 

 times, and the ethereal solution evaporated to dryness : the residue weighed 0*9401 grms. 

 The residue from the ether treatment was boiled with alcohol, the solution filtered and eva- 

 porated to dryness, when 2'4420 grms. of crude oxide of tribenzyl phosphine were obtained. 



There remained after the treatment with alcohol 1*1233 grms. of insoluble matter, 

 which was proved to contain the substance we have called above " Insoluble crystalline 

 body." 



* At first we thought it possible that the dibenzyl phosphinic acid might have owed its origin to the action of the 

 potash solution on oxide of tribenzyl phosphine (see p. 558). But that this reaction does not occur when oxide of tri- 

 benzyl phosphine is boiled with caustic potash solution, we proved by an actual experiment. 



