BENZYL PHOSPHINES AND THEIR DERIVATIVES. 549 



The experiments just described shows that the reaction is of a highly complex nature, 

 and that it varies with the conditions of the experiment. 



As the substances resulting from the reaction were obtained in very small quantity, 

 barely sufficient for their analysis, we were unable to study their properties, and must 

 remain in doubt regarding their exact nature. 



Action of Sulphur on Monobenzyl Phosphine. — A preliminary experiment showed 

 that no action occurs in the cold, but on warming the two bodies together the sulphur 

 dissolves and abundance of sulphuretted hydrogen escapes. 



About 4 grms. of the phosphine were placed in a test-tube full of carbonic anhydride, 

 and heated by immersing the tube in a water-bath. Powdered sulphur was then added, 

 and sulphuretted hydrogen was evolved in abundance — to such an extent, indeed, that 

 at one time the liquid frothed over into the water-bath. Excess of sulphur was added to 

 the liquid, which had thus frothed over (B), and the same was done with the liquid in 

 the tube (A) — a very considerable quantity being required in both cases. 



As soon as the evolution of sulphuretted hydrogen ceased, the liquid was allowed to 

 cool. It was colourless and viscous. It was boiled with water, when sulphuretted 

 hydrogen was again evolved — nearly the whole (of the viscous liquid) dissolved, forming 

 a strongly acid solution. This was neutralised with baryta, and the solution heated, 

 when a crystalline salt separated very much like benzyl phosphinate of barium, and was 

 at first considered to be that substance. 



The product B gave a similar salt. The two salts were purified by dissolving them in 

 cold water and then heating the solution when they were deposited in the crystalline state. 



Analysis of Barium Salt from A. 



0-4710 gave 03184 BaS0 4 = 0187213 Ba = 3975 per cent. 

 04710 lost at 110° C. 00253 H 2 = 537 



Analysis of Barium Salt from B. 



0-5691 gave 0-3878 BaS0 4 = 0228019 Ba =4006 per cent. 

 0-5691 lost at 110° C. 00289 H,0 = 507 ;, 





Obtained. 



Calculated for (C 7 H 7 )P 





A. B. 



Barium, 



39-75 4006 



4017 



Water, 



5-37 507 



527 



On attempting to obtain the acid by decomposing the barium salt with sulphuric 



acid, sulphuretted hydrogen was evolved — no doubt, with formation of benzyl phosphinic 



acid — 



C 7 H 7 P0 2 SH 2 + H 2 = C 7 H 7 P0 3 H 2 + H 2 S . 



The results of this experiment indicate that when the phosphine is warmed with 

 sulphur, pyro-benzyl-thio-phosphinic acid is formed, 



2C 7 H 7 PH 2 + 5S = (C 7 H 7 ) 2 P 2 S 5 H 2 + H 2 S , 



