Mr. E. A. Parnell on Sulphocyanogen. 259 



terest with which the products of its decomposition by alkalies 

 will be viewed, is materially lessened. For this reason I have 

 not pursued this subject so completely as I intended, nor, 

 perhaps, as it deserves. Although I have been led by a point 

 in this investigation, which I could not comprehend, to the 

 discovery that sulphocyanogen, if not exactly so composed as 

 I have represented it, is certainly not the radical of the sul- 

 phocyanides, but a product of its decomposition ; yet the 

 point in question has not been ascertained, namely, the 

 changes that sulphocyanogen undergoes by alkalies. 



At first I imagined the black substance which separated 

 from the solution of sulphocyanogen in alkali, on cooling, and 

 the brown or black substance precipitated by acids, insoluble 

 in water and alcohol, as accidental or merely secondary pro- 

 ducts : I now look on these differently. When the last brown 

 substance is digested again in an alkali, more hydrothiocyanic 

 acid is separated ; the remainder is quite black, and is evi- 

 dently identical with the first black substance. It appears 

 more to resemble paracyanogen than anything else with 

 which I am acquainted ; but not having obtained it pure, and 

 but in small quantity, I have not been able to decide this 

 point. Sulphocyanide of potassium, and sulphite of potash, 

 are likewise formed when sulphocyanogen is digested in pot- 

 ash, but the sulphite is in very small quantity, and I believe 

 accidental. 



Hydrothiocyanic acid is not produced by potash and soda 

 only; barytes. ammonia, and even the alkaline carbonates 

 give birth to it. Its production by ammonia is remarkable. 

 The sulphocyanogen becomes light yellow, but is not dis- 

 solved; sulphocyanide of ammonium, with only a trace of 

 thiocyanide, is formed. The yellow substance into which the 

 sulphocyanogen is converted is, however, hydrothiocyanic 

 acid. 



This proves that whatever may be the action of the alkali, 

 it is not the affinity of its radical for the radical of the acid 

 (or as it may be called, thiocyanogen) which is the leading 

 cause ; for if so, the whole of the acid should have existed as 

 thiocyanide of ammonium. 



It is also probable that the action is an oxidizing one, for 

 I find that the acid is produced by the action of chlorine and 

 nitric acid on sulphocyanogen. Indeed, it is difficult to pre- 

 pare sulphocyanogen by nitric acid without its production, 

 and hence I have recommended that prepared by this means 

 as preferable to that by chlorine for the preparation of this 

 acid *. It has been observed, that when chlorine is passed into 



* If a mixture of sulphocyanogen and hydrothiocyanic acid be digested 



S 8 



