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



Treated with caustic potash, all the salts of tri-ethyl phosphorus betaine yield tri- 

 ethyl phosphine oxide, 



(C 2 H 5 ) 3 P<(g H _ COOH + 2KHO = (C 2 H 5 ) 3 PO + KX+H 2 + CH 3 -COOK . 



Several of the tertiary phosphines combine directly and energetically with a molecule 

 of bisulphide of carbon to give highly characteristic compounds, usually of a red colour, 

 and possibly having the constitution, 



■0 



R 3 P< 



So characteristic and so readily formed is this compound in the case of tri-ethyl phos- 

 phine, that its production may be employed as a test either for bisulphide of carbon or 

 for the phosphine itself. As yet these (bisulphide) compounds have been obtained only 

 with methyl, ethyl, and iso-propyl phosphine, and with those of the aromatic phos- 

 phines containing ethyl or methyl groups. 



According to Czimatis, # these mixed phosphines combine very easily with bisulphide 

 of carbon if they contain methyl, the readiness with which combination occurs diminish- 

 ing however, in proportion to the molecular weight of the aromatic radical, while, if they 

 contain ethyl, combination occurs only slowly and with difficulty. HoFMANNt has 

 somewhat exhaustively studied the compound of tri-ethyl phosphine and the bisulphide, 

 which forms with explosive violence. Among its properties are the following : — It is 

 insoluble in water, difficultly soluble in ether, but easily dissolves in hot alcohol, from 

 which it separates on cooling in red needles like chromic anhydride. From an ethereal 

 solution it is deposited by spontaneous evaporation in large deep red monoclinic crystals 

 exhibiting dichroism, which melt at 95° and volatilise at 100°. It is soluble in strong 

 hydrochloric acid, and if the solution is mixed with platinic chloride, a yellow amorphous 

 compound is produced, 2(C 2 H 5 ) 3 PCS2,PtCl 4 . With silver oxide or nitrate, it is decomposed 



as follows : — 



(C 2 H 5 ) 3 PCS 2 +2Ag 2 = Ag 2 S+Ag 2 + C0 2 +(C 2 H 5 ) 3 PS ) 



and moist air produces a similar change. But if it is heated with water to 100° C, the 

 following reaction occurs : — 



4(C 2 H 5 ) 3 PCS 2 + 2H 2 = 2(C 2 H 5 ) 3 PS + (0 2 H 6 ) 3 PO + (C 2 H 5 ) 3 (CH 3 )POH + 3CS 2 . 



Heated with sulphuretted hydrogen, it suffers the following change — 



3(C 2 H 5 ) 3 PCS 2 + H 2 S = 2(C 2 H 5 ) 3 PS + (CH 2 S)(C 2 H 5 ) 3 PCS 2 + CS 2 . 



The action of halogens upon tertiary phosphines has not been very fully studied. 

 Probably direct addition would occur in all cases. This has been proved to take place 

 with tri-ethyl phosphine if the halogen is allowed to act very gradually upon it. The 

 chloride (C 2 H 5 ) 3 PC1 2 thus obtained is crystalline, melting at 100° and volatilising readily, 



* CV.imatis Berichte, xv. (1882) p. 2016 t Hofmann, Phil. Trans., I860, p. 431. 



