510 



Dr. H. E. Armstrong on 



[June 16, 



The following simple equation, therefore, explains the reaction which 

 has taken place : — 



cs 2 + so 3 = COS + so 2 + s. 



Action of Sulphuric Anhydride on Phosphorous Chloride* 



The ease with which the foregoing reaction had taken place led me to 

 try the action of the anhydride on a compound which, possessing latent 

 affinities and a predisposition to combine with oxygen, it was to be expected 

 would cause the separation of the " extraradical " oxygen atom, as I term 

 the atom which is signalized by its great mobility. The compound chosen 

 was phosphorous chloride. 



On adding this to the anhydride, which must be in a flask surrounded 

 by ice, a violent reaction takes place, attended by a copious evolution of 

 sulphurous anhydride. No further action is observable after equal equi- 

 valents have been employed ; and on distilling the resulting liquid and 

 fractioning two or three times, two products are obtained, the one boiling 

 from 1 10° to 1 14°, which, from all its properties, is undoubtedly phosphoric 

 oxychloride. 



The reaction has therefore partly taken place as was expected, and 

 according to the equation — 



PCI3 + S0 3 = POCI3 + S0 2 . 



The second product, which is obtained in varying quantity, according as 

 more or less anhydride is employed, the more being formed, the greater 

 the proportion of the latter *, boils at the first distillation between 120° and 

 170°, and cannot be obtained of constant B.P., even by repeated rectifica- 

 tion, by each of which it only suffers further decomposition, a thick varnish- 

 like residue remaining every time. This product contains phosphorus, 

 chlorine, and sulphur. 



H. Rose, who also studied this reaction, though without observing the 

 formation either of phosphoric oxychloride or of sulphurous anhydride, 

 which latter he only remarked was given off on subsequent distillation, also 

 describes this second product ; he ascribes to it, however, an exceedingly 

 complicated formula. 



It is very possible that a further substitution of chlorine by oxygen has 

 taken place, as explained by the equation — 



POCl 3 + 2S0 3 = P0 2 C1 + S 2 0 5 C1 2 ; 



and this compound can be viewed as metaphosphoric chloride, which it is 

 to be expected would be of a very unstable nature. The above product is 

 then, on this supposition, a mixture of two chlorides, to decide which it 

 will be first necessary to institute experiments with pure phosphoric oxy- 



* It is probable that only phosphoric oxychloride would be formed were the experi- 

 ment reversed, and the anhydride allowed to act on an excess of the phosphorous 

 chloride, 



