3-iS Materials for a History of the Prussiates. 



■?; :tr>i ibe bases of the sulphate, of the muriate, and of 



t white prussiate, loses all its activity with respect to the 

 black oxide in question,: but still, neither the application of 

 the honing nitric acid, nor the oxygenated muriatic acid, can 

 succeed in raising the oxidation of this last. These acids 

 may in fact destroy Prussian blue, and even reduce it to red 

 oxide : but while there remains some blue to be destroyed, 

 this last will preserve to the end the black oxide in all its 

 primitive integrity. 



If we treat the red oxide with prussic acid, we shall form 

 no kind of combination : — this is conformable to the obser- 

 vation of Scheeie : but if we make use of black oxide, we 

 shall obtain greenish prussiate which the air will convert 

 into perfect blue. The black oxide enters therefore into 

 the combination of Prussian blue. If this oxide was not 

 necessary 1 , or if the red oxide could exclusively serve as a 

 base to Prussian blue, we do not see why this oxide, and 

 even its solution, mixed with simple prussiate of potash, 

 would not give Prussian blue. 



I have remarked a little higher that the affinity of the 

 prussic acid for this dose of black oxide, which renders it 

 proper for producing triple prussiate, might be powerful 

 enough for saving it from the destiny common to all the ox- 

 ides which are combined with acids in general. 



It appears to me, in short, that we draw this consequence 

 from the following experiment : 



Throw into a flask hydrosulphuret of potash upon Prus- 

 sian blue, and keep the mixture well corked : in a few days 

 we find the hydrosulphuret converted into triple prussiate, 

 and the red oxide of Prussian blue alone changed into black 

 hvdro;ulpir.;ret : and hence we see that if the red oxide has 

 followed the example of all the oxides when the hydrosul- 

 phuret finds them united to acids, it is not so with the 

 black oxide, which, as we have so frequently said, passes 

 from the triple prussiate of potash into the Prussian blue. 

 This oxide, as it wt-re, forms a separate stripe ; it never 

 participates in the changes of which the red oxide is sus- 

 ceptiblr, which is the base of Prussian blue. 



H\dro-arJp!'areUtd water brings the Prussian blue to the 



state 



