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



and this with water is decomposed into mono-thio-phosphinic acid, with evolution of 

 -ulphuretted hydrogen, 



(C 7 H 7 ) 2 P 2 S 5 H 2 + 6H 2 = 2C 7 H 7 PS(OH) 2 + 5H 2 S . 



In a second experiment we attempted to obtain derivatives of the pyro acid. A 

 quantity of the phosphine was heated as before with excess of sulphur until sulphuretted 

 hydrogen ceased to be evolved. The product deposited a minute quantity of colourless 

 plates, which were not obtained in sufficient quantity for analysis. 



A quantity of the product was boiled with a solution prepared by saturating barium 

 hydrate with sulphuretted hydrogen, and then adding an equal quantity of the hydrate. 

 Sulphuretted hydrogen was evolved, and when the solution had become very concen- 

 trated, it deposited colourless crystals on cooling, which were collected and analysed. 



Analysis. 



0T516 i lost at 110 ° C> °' 0096 = 6 * 33 P er cent water - 



j gave 00647 BaS0 4 =0 038042 Ba = 2509 per cent, barium. 





Obtained. 



Calculated for (C 7 H 7 ) 3 P 2 S 3 OoBa,2H 2 



Barium, . 



25-09 



2513 



Water, 



6-33 



6-60 



The production of the pyro acid is thus to a certain extent confirmed, its barium 

 salt, which is no doubt formed in the first instance, being subsequently decomposed by 

 water, thus — 



(1) (C 7 H 7 ) 2 P 2 S 5 H,+BaS = (C 7 H 7 ) 2 P 2 S 5 Ba +H 2 S 



(2) (C 7 H 7 ) 2 P 2 S 5 Ba+ 2H 2 = (C 7 H 7 ) 2 P 2 S 3 2 Ba+ 2H 2 S . 



We may also mention, that on dissolving the product of the action of sulphur on the 

 phosphine in alcohol and adding mercuric chloride, a white amorphous precipitate was 

 produced in abundance. We did not analyse it, as it darkened slowly on drying. 



We have already mentioned that Michaelis studied the action of sulphur on phenyl 

 phosphine and obtained two products — a liquid (C 6 H 5 )PH 2 S, and a solid (C 6 H 5 P) 3 S. The 

 experiments we have just described show that benzyl phosphine behaves in a totally 

 different manner, and they also prove that sulphur and oxygen do not react in an 

 analogous manner upon a primary phosphine. 



Action of Halogens on Monobenzyl Phosphine. — If bromine is mixed with the 

 phosphine an explosive action occurs, and torrents of hydrobromic acid are disengaged. 

 But when the vapour of bromine comes in contact with the base, the action proceeds 

 quietly, and a white solid is produced. If both the bromine and phosphine are dissolved 

 in glacial acetic acid, the reaction is completely under control. If the vessel in which 

 the mixture is made is kept cool and the bromine gradually added, a colourless crystalline 

 salt is produced, and its amount increases as the bromine is added, up to a certain point, 

 but it then diminishes. 



