BENZYL PHOSPHINES AND THEIR DERIVATIVES. 619 



heating the acid with crystalline phosphorous acid, in the hope that a reaction would 

 occur according to the following equation : — 



SHgPOs+CyH^POs^SHgPO.+CyH^P, 



which would be analogous to the reaction which phosphorous acid suffers when heated 



alone — ■ 



4H 3 P0 3 = 3H 3 P0 4 + PH 3 . 



Accordingly, 5 grms. of benzyl phosphinic acid were mixed with a large excess 

 (20 grms., the calculated quantity being only 7"1 grms.) of crystallised phosphorous 

 acid, and the mixture heated in a distilling flask. It soon fused to a clear liquid, and 

 then a little water came off. Presently the mass began to disengage phosphuretted 

 hydrogen, and to froth considerably. After some time an oily liquid distilled, which was 

 colourless, and finally decomposition and charring occurred. The whole of the liquid 

 distillate was redistilled, and gave 1'3 c.c. of an oil having the smell and properties of the 

 primary phosphine. The reaction seems then to proceed in the desired manner, and if 

 the whole of the liquid obtained consisted of the phosphine, the yield was nearly 50 per 

 cent, of the theoretical quantity. In all probability other phosphinic acids would be 

 reduced by phosphorous acid, and, if so, the action is of some importance, as we believe 

 that no other method for their reduction has yet been discovered. 



Action of Pentachloride of Phosphorus on Benzyl Phosphinic Acid. — We were 

 anxious to obtain the two chlorides, (C 7 H 7 )C1HP0 2 and (C 7 H 7 )C1 2 P0. 



10 grms. of the benzyl phosphinic acid and 14 grms. of pentachloride of phosphorus 

 were mixed in a distilling flask, when a pretty brisk action occurred spontaneously, the 

 mixture growing very hot and torrents of hydrochloric acid coming off. As soon as the 

 action had moderated, the mixture was heated, and 8 grms. of liquid were obtained dis- 

 tilling below 110° C. The residue in the flask was allowed to cool, and hardened into a 

 brown viscous mass. It was then heated, when the thermometer rose slowly to 300° C, 

 during which a colourless liquid distilled. There remained in the flask a black liquid, 

 which solidified to a hard resin, and which contained free phosphorus. The distillate 

 boiling from 110°-300° C. was in too small a quantity to redistil, but it probably con- 

 tains one of the two chlorides, for when left for some time in contact with the air, it was 

 converted into a crystalline mass, presumably benzyl phosphinic acid. The reaction was 

 not sufficiently definite to invite further investigation. 



(3) Dibenzyl Phosphinic Acid, (C 7 H 7 ) 2 HP0 2 . 



We have obtained this acid by the second and third reaction described at the beginning 

 of this part of our paper, and also by fusing the tertiary phosphine oxide with caustic 

 potash. To isolate it from the products of the reaction occurring between phosphonium 

 iodide, zinc oxide, and benzyl chloride, the contents of the sealed tubes, after having been 

 steamed with water to drive off the primary phosphine, are boiled for a long time with 



