11300 



grms. 



•9401 



» 



24420 



>> 



11223 



)> 



506 PROF. LETTS AND MR R. F. BLAKE ON 



Tabulating the above results, we obtained by oxidising 5 "6 75 5 grms. of the crude 

 product, 



Crude dibenzyl phosphinic acid, ...... 



Substances soluble in ether, ...... 



Crude oxide of tribenzyl phosphine, ..... 



Substances insoluble in alcohol (containing " insoluble crystalline body"), 



56344 



The weight of dibenzyl phosphinic acid corresponds roughly with 20 per cent, of 

 dibenzyl phosphine, and that of the oxide of tribenzyl phosphine with about 50 per 

 cent, of tribenzyl phosphine. The experiment confirms former results, and shows that 

 the product is a complex mixture, but is composed mainly of the two phosphines. 



Having thus definitely proved that the two phosphines are produced in Hofmann s 

 reaction, we had next to devise a method for separating them from each other and for 

 isolating them in the pure state. We had already tried fractional distillation, and had 

 failed in accomplishing the desired object ; we had also tried, though without any large 

 measure of success, to isolate the tertiary phosphine by crystallising it from alcohol. The 

 experiment had indeed left us somewhat in doubt as to whether it is a solid or a viscous 

 liquid. At the time, however, we had only a very crude and impure product at our dis- 

 posal, containing a large quantity of oxide of tribenzyl phosphine ; whereas now we had a 

 product, comparatively speaking, pure and free from that substance. As no other method 

 could be devised for isolating the tertiary phosphine, we decided once more to see whether 

 it was a solid substance capable of being crystallised from alcohol. Accordingly the 

 remainder of the product, some 50 grms., was first treated with a somewhat large quantity 

 of ether, when a considerable quantity of " insoluble crystalline body " was obtained. 

 It was perfectly colourless, and weighed when dry 2 grms. The ethereal extract was 

 filtered from this, and again diluted with ether, to see whether any more insoluble crystal- 

 line matter would be precipitated, but the solution remained clear. The ethereal solution 

 was then distilled to dryness in a current of carbonic anhydride, and alcohol added to the 

 hot solution in such quantity that the mixture when boiled gave a clear solution, with only 

 a few oily drops. This mixture (contained in a flask full of carbonic anhydride) deposited 

 on cooling a good deal of a viscous liquid, and then after about twenty-four hours' rest a 

 considerable quantity of minute colourless crystals separated, which when examined with 

 a lens appeared to be thick quadratic plates. 



The following experiments were made with portions of the crystals : — 



(1) Warmed with crystallised iodide of benzyl, reaction occurred, and iodide of tetra- 

 benzyl phosphonium was obtained. 



(2) The crystals seemed to be volatile without decomposition. 



(3) They were soluble in ether, but on exposure to air the solution grew turbid rapidly, 

 and needle-shaped crystals separated out, which had the characteristic form of oxide of 

 tribenzyl phosphine, and which gave its characteristic compound when treated with a 

 solution of bromine in acetic acid. 



