Chemical Science. 211 



driving off a portion of the carbonic acid, and forming a kind 

 of double salt in which it may be presumed ^ of the potassa 

 is combined with the oxide of copper, and ^ with the carbonic 

 acid. Water decomposes this combination, dissolving the 

 caustic and carbonated alkali, and leaving the oxide of 

 copper free. 



Hence it became necessary to analyze a salt, the base of 

 which would not retain carbonic acid, and that formed by lead 

 was selected for the purpose. A certain quantity of this salt 

 was heated with twenty-hve times as much peroxide of copper, 

 and yielded a mixture of 2 volumes of carbonic acid, and 1 volume 

 of nitrogen. The quantities of the gases were such, as to give 

 for 100 parts of the salt 11.05 of carbon, and 12.84 of nitrogen, 

 or together 23.89 of cyanogen. This added to the weight of 

 the other elements of the salt employed, surpasses the whole 

 weight by 6.19, supposing the bases are in the state of oxide ; 

 but, if the prussiate be considered as composed of 1 atom of 

 cyanuret of iron, with 2 atoms of cyanuret of lead, then the 

 weight of the cyanogen, the iron, and the lead, would be almost 

 exactly what it ought to be. 



To prove that, in this compound, the metals were not in the 

 state of oxides, sulphuretted hydrogen was passed over it 

 in the heated state ; no water was formed but hydrocyanic acid, 

 protbsulphuret of iron, and sulphuret of lead, were produced ; 

 and the weights of the products agreed as exactly as possible 

 with the theoretical view taken of its composition, which is as 

 follows : 



98.61 100 



The composition of the ferro-prussiate of potassa will be 

 1 proportion or atom of cyanuret of iron, 2 of cyanuret of 

 potassium, and 6 of water, or. 



Iron . . 12.85 = Protoxide of iron . . 16.54 • 



Potassium 37.11 =. Potassa 44.68 



Cyanogen 37.22 



Water . . 12.82 



The composition of the other two salts is exactly analogous, 

 the quantity of water only varying. 



These experiments prove, that the salts called prussiates, or 

 ferruginous hydrocyanates, are really cyanurets, composed of 

 1 atom of cyanuret of iron, and 2 atoms of cyanuret of the 

 P 2 



