﻿Skey. — New process for maldng Sulpho-cyanide of Potassium. 331 



product may have the degree of pmity required ; thus we have first the 

 formation of the crude article, by heating to tranquil fusion dry ferro-cyanide 

 of potassium with sulphur, and this product has to be treated in various ways 

 in order to remove sulpho-cyanide of iron, alkaline sulphides, etc., from the 

 salt in request. 



The processes, therefore, necessary to accomplish this purification must 

 largely add to its cost. To save this expenditui-e in labour and material I 

 have sought to effect the economical manufacture of this salt by the application 

 of a process or reaction which I have taken advantage of in discriminating 

 the state in which sulphur exists on the sui-faces of sulphurized gold.* This 

 process consists in applying cyanide of j)otassium to such compounds at common 

 temperatures, when any sulphur present in a free state woiild combine with it 

 to form a sulpho-cyanide, but if present as a sulphide would only be transformed 

 into a soluble sulphide. 



In my first experiments, however, for the purpose of pi'eparing this salt 

 direct from cyanide of potassium and common flour of sulphur, I found that 

 unless the temperature of the mixture was raised considerably, only a veiy 

 small portion of the sulphur was taken up, and the product was then contami- 

 nated with the impurities I designed to omit. 



This refusal of sulphur to combine freely with the cyanide at common 

 temperatures was, I found, entirely due to the presence of some gas, probably 

 air, which substance may readily be got rid of, as will suggest- itself, by pouring 

 the sulphur into boiling water and keeping up ebullition for a few minutes. 

 When the water and sulphur is quite cooled down the cyanide may be added 

 to the sulphur in an equivalent proportion. 



The quickest way to effect the combination is to suspend the wet sulphur 

 in a porous bag near the top of the cyanide solution, when in a few days the 

 combination will be complete, and a product obtained comparable in purity 

 with that of the cyanide used. I need not state that the operation should be 

 carried on in an air-tight vessel. 



It is absolutely necessary that the cyanide used should be free from caustic 

 alkali, otherwise sulphides would be generated ; it is but rarely, however, that 

 cyanide is thus contaminated. 



If the precautions indicated are taken, the product is sufficiently pure for 

 use in aU the ordinary applications to which this salt is put in the laboratory. 



See Trans. N.Z. Inst., Vol. III., p. 21G. 



