THE 



PHILOSOPHICAL MAGAZINE 



AND 



ANNALS OF PHILOSOPHY. 



[NEW SERIES.] 



JUNE 1831. 



LIX. On a Combination ofBicyanide of Mercury and Iodide 

 of Potassium. By JAMES APJOHN, M.D. Professor of Che- 

 mistry to the Royal College of Surgeons in Ireland. 



To the Editors of the Philosophical Magazine and Annals. 



Gentlemen, 



1LTAVING recently, in the course of some experiments upon 

 "*-* the salts of mercury, fallen upon a new, and, in some 

 respects, a rather remarkable compound, I beg leave to com- 

 municate to chemists, through your Journal, the following 

 brief notice of it. 



When liquid hydriodate of potash is added to a solution of 

 corrosive sublimate, the well-known biniodide of mercury im- 

 mediately falls down. This is a decomposition familiar to every 

 chemist. But if for corrosive sublimate we substitute the bi- 

 cyanide of mercury, notwithstanding the analogy in composi- 

 tion between these two salts, no such double exchange of 

 principles takes place. A precipitate however in this case 

 also slowly forms, possessing the following properties. It 

 occurs in very thin four-sided prisms, of a beautiful pearly 

 aspect. These are very soluble in hot water, but this fluid 

 scarcely acts upon them at the temperature of 60. Digested 

 with ammonia and potash they appear to experience no change; 

 and the same may be said of them when brought into contact 

 with the alkaline carbonates. When touched however with 

 a drop of muriatic acid, their colour is immediately changed 

 to a bright scarlet, and the odour of prussic acid is evolved. 

 A portion of them ignited in a platinum crucible left a residuum 

 which, when dissolved in water, gave a copious crystalline 

 precipitate with tartaric acid added in excess. 



From these experiments, and several others which it is 

 N.S. Vol. 9. No. 54. June 1831. 3 F unnecessary 



