252 



Red oxide of 

 mercury de- 

 composes both 

 prussiates of 

 potash. 



Prussiate of 

 mercury not 

 decomposed 

 by sulphuric 

 acid diluted, 



or by nitric ; 



but it is by the 

 muriatic. 



Soluble in pot- 

 ash. 



Decomposed 

 by muriate of 

 tin, and hidro- 

 sulphuretted 

 water; 



HISTORY OF PRUSSIATES. 



The ved oxide of mercury equally decomposes the simple 

 prussiate. The potash too is separated from it ; and as this 

 has no action on the prussiate of mercury, the prussiate cry- 

 stallizes amidst it. It likewise decomposes the triple prus- 

 siate completely, but this requires long- boilings. In this 

 process, the black oxide in the triple prussiate passes to the 

 state of red oxide, and is deposited as an ochre. Part of the 

 mercury gives out the oxigen requisite for this, and hence 

 it is found in the metallic state among the ochre precipi- 

 tated ; but without this superoxigenation of the iron, which 

 diminishes the affinity of this metal, the oxide of mercury 

 probably would not decompose a combination so solid as that 

 of the triple prussiate. 



The aqueous sulphuric acid has no action on prussiate of 

 mercury, even with heat. Not the slightest smell of prussic 

 gas is given out. 



Potash saturates the sulphuric acid as a vehicle of tl*e 

 prussiate, but occasions no precipitate. 



Concentrated sulphuric acid destroys the prussic, gives out 

 sulphurous acid, and thus destroys all means of comparison. 



Nitric acid is not more successful even with boiling. At 

 the beginning, indeed, a little nitrous gas is perceived; but 

 this, no doubt, is occasioned by the black oxide of iron con- 

 tained in the prismatic prussiate. The prussiate, however, 

 crystallizes in the midst of the acid; and alkalis saturate 

 this acid without precipitating any thing. 



But it does not elude the action of the muriatic acid in 

 like manner. There is a separation of prussic gas, a com- 

 plete decomposition, and the prussiate is totally changed 

 into corrosive sublimate. Accordingly, alcohol dissolves 

 the saline residuum of this process completely; and we find 

 nothing but sublimate on trying it by reagents. It is well 

 known, that alcohol does not dissolve the prussiate of mer- 

 cury. 



Potash dissolves the prussiate of mercury abundantly, by 

 the assistance of heat; and this salt crystallizes in it on cool- 

 ing. Alcohol separates it too, and it is found entire. 



Muriate of tin at a minimum, and hidrosulphuretted wa- 

 ter, decompose this prussiate instantly, and the prussic acid 

 is set free. 



It 



