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



Under favourable circumstances, from 60-70 grms. of crude monobenzyl phosphine 

 were obtained from 360 grms. of benzyl chloride ; or, in other words, each tube yielded 

 a little over 2 grms., consequently the preparation of even the crude phosphine in any 

 quantity is extremely tedious and troublesome. 



The residue in the flask A always contained in addition to water, a brown viscous and 

 insoluble liquid, which as a rule solidified on cooling. Both it and the water contained 

 phosphorised benzyl derivatives. We shall first discuss the properties of the primary 

 phosphine, and afterwards the nature of the various bye products, and the methods we 

 employed for isolating them. 



Monobenzyl Phosphine. — Hofmann purified the crude phosphine by fractional distilla- 

 tion only. He states that after two rectifications in a stream of hydrogen it is obtained of 

 the constant boiling point 180°. 



Our own experiments, repeated again and again, and with the greatest care, have 

 satisfied us that the pure phosphine cannot be readily obtained thus. We have at 

 different times operated upon two to three hundred grams, and have invariably obtained 

 the same results on fractionating it. The crude phosphine begins to boil at about 100°, 

 the thermometer then rises rapidly to 160°, and from 160°-190° most passes over. The 

 residue in the distilling flask decomposes if the distillation is pushed further, and red 

 phosphorus separates. All the fractions contain the phosphine, for they all have its 

 powerful and characteristic odour, and when mixed with fuming hydriodic acid they 

 give its crystalline hydriodate. After repeated rectifications, the lower boiling fractions 

 resolve themselves into a liquid, boiling at 110°-1 16°, which is no doubt toluol, while 

 the high boiling fractions pass over from 175°-185°, the thermometer being fairly 

 constant at 180°-183°. 



We have investigated the high boiling residue (above 190°), and give the results on 

 p. 585. 



In view of the difficulty experienced in separating the primary phosphine by simple 

 distillation, in a pure state, we decided to obtain the crystallised hydriodate from the 

 crude product, and from it the phosphine, but, owing to the bulky nature of that 

 compound (i.e., the hydriodate) and its insolubility, we experienced considerable difficulty 

 in effecting this. After several experiments, we found that either of the two following 

 methods might be employed : — 



( 1 ) The crude phosphine was placed in a retort, and a stream of pure, dry, hydriodic 

 acid gas was conducted by a long tube into the body of the retort. As soon as saturation 

 appeared to be complete, the retort was heated gradually in an oil-bath to a temperature 

 of 160°-180°, a slow current of hydriodic acid passing all the time. The hydriodate then 

 sublimed in beautiful colourless scales, and when most had thus volatilised into the neck 

 of the retort, the latter was allowed to cool, the hydriodate shaken out, and well washed 

 with pure benzol. 



(2) The crude product was mixed with about twenty times its volume of pure dry 

 benzol, and the mixture saturated with dry hydriodic acid. It grew warm, and eventually 



