Materials for a History of the Prussiales. 43 



Titanium. Simple ditto: yellow oxide of iron, such as 

 the prussiate gives with the solution* of red oxide. I have 

 never yet been able to obtain titanium exempt from iron. 



Uranium. Triple prussiate : precipitate of a blood colour. 



Uranium. Simple: whitish yellow. v 



Cobalt. Triple prussiate : precipitate of a grass green. 



Cobalt. Simple : clear cinnamon colour. 



Nickel. Triple prussiate : greenish white precipitate. 



Nickel. Simple : yellowish white. 



Manganese. Triple prussiate : precipitate of a pea-bloom 

 colour. 



Manganese. Simple : dirty yellow. 



Copper. Triple prussiate : a fine crimson. 



Copper. Simple : yellow. 



White muriate of copper, or muriate the oxide of which 

 is at the minimum dissolved in muriatic acid. — Triple prus- 

 siate : white precipitate, red inclined to crimson. We find 

 that if this muriate was perfectly exempt from oxide at the 

 maximum, the precipitate would be white. The solution 

 of this muriate is like that of iron ; it is difficult to keep it at 

 the zero of hyper-oxidation, on account of the air. 



The same muriate : simple prussiate : curdled precipitate, 

 perfectly white. Some drops of potass take the prussic acid 

 from it, and restore the yellow colour to it, which is the 

 colour of the oxide of copper at the minimum* 



Platina and the two prussiales : nothing. 



Prussiate of Mercury .• — This is obtained, as we already 

 know, by treating the red oxide of mercury with Prussian 

 blue. This salt crystallizes easily in tetrahedral prisms. 



It is always opaque. It may contain potash, as we shall 

 see presently, if there was any in the Prussian blue. It also 

 contains oxide of iron ; we may perceive this from the fol- 

 lowing experiment : 



Heat some grains with muriatic acid in a small matrass, 

 and white prussiate is precipitated. 



In order to purge it from iron, we must boil its solution 

 over red oxide several times : at every boiling it deposits 

 oxide of iron ; but this depuration is very tedious. 



The prussiate of mercury changes its state on passing over 



the 



