1870.] 



Acids of the Sulphur Series. 



505 



Calculated. Found. 



S 2 = 64 297 29*56 



Cl a = 71 33-0 32-80 



0 5 = 80 — — 



215 



The formation of this chloride, and of carbonic oxychloride, is explained 

 by the following equation : — 



CC1 4 + 2SG 3 = COCl 2 + S 2 0 5 C1 2 . 



This body, which I, for reasons to be mentioned later on, call pyrosul- 

 phuric chloride, was first discovered by H. Rose, who, in his description of 

 its properties, especially calls attention to its being but slowly decomposed 

 in contact with water at ordinary temperatures, — a statement which I can 

 thoroughly endorse. 



Schiitzenberger *, however, who in the meantime has also published a 

 series of observations on this reaction, with which on the whole mine agree, 

 differs very considerably in his description of this chloride, which, accord- 

 ing to him, boils at 130° Ct, and is decomposed immediately by water. 

 On this he lays particular stress, and draws the conclusion that either his 

 substance is isomeric with Rose's, or that Rose worked with an impure 

 substance. 



It seems to me, however, that the contrary is the case, — that Rose 

 describes the properties of the pure substance, although, to judge from his 

 analyses, his was not a chemically pure one. To make the chlorine and 

 sulphur estimations, I broke a very thin glass bulb, filled with a weighed 

 quantity of the liquid, under water ; but so great is the relative stability of 

 the chloride, that a considerable time elapsed before the small quantity 

 employed was decomposed, even when I used a dilute potassa solution, 

 which was warmed to 50°-60° C. 



The direct substitution of two chlorine atoms by one oxygen atom, which 

 has taken place in carbonic tetrachloride, is, as far as I know, the first in- 

 stance of this nature among organic compounds. The formation of phos- 

 phoric oxychloride from phosphoric chloride by means of sulphuric 

 anhydride is, I believe, the only analogous reaction, — 



PCL + S0 3 =POCl 3 + S0 2 C1 2 . 



The contrary substitution is often enough met with — is, in fact, one of 

 the general reactions of phosphoric chloride. Thus we have : — 



{ H fr ° m { I} { from { co6i and { o'S: from { cocv 



It may be predicted that carbonic tetrabromine treated in the above 



* Compt. Rend, lxix. p. 350. 

 t Rose gives 145° C. as the B.P. 



