5% Materials for a History of the Prussiates* 



V akest of all, is sufficient to decompose them. In a word, 

 its combustibility, taste, aromatic smell, its being gene- 

 rated in the m ; st of volatile oils, and its preservation in 

 alcc.hol, exhibit qualities which much more strongly re- 

 semble oily and inflammable productions than saline sub- 

 stances. 



The prussic acid, notwithstanding its trifling saline 

 energy, has a powerful action on the major oxide of mer- 

 cury : it furnishes with this oxide a saline combination, 

 so well characterized in its attributes, that we are compelled 

 to acknowledge that it acts in certain circumstances like the 

 most powerful acid. Nothing in fact is wanting to the prus- 

 siate of mercury, to entitle it to be ranked among the most 

 perfect of metallic salts : it will perhaps astonish some che- 

 mists, to see that it refuses to be united to the minor oxide; 

 but by a concurrence of affinities, of which we have other 

 examples, it raises it to the state of major oxide, by elimi- 

 nating a part of the metal, in order to form, with the other, 

 prussiate of mercury. 



The prussic acid has no action upon the red oxide of iron ; 

 but it attacks the black oxide, and produces white prussiate 

 with it. This prussiate, it is true, is not absolutely white, 

 the difficulty of preparing, with green sulphate, a pre- 

 cipitate at the zero of hvper-oxidation, not permitting it : 

 thus, it is always greenish ; but as, upon drying, it becomes 

 perfect Prussian blue, we cannot doubt that the prussic acid, 

 plus the base of the green sulphate, will give, all perturba- 

 tion being out of the question, a prussiate equally white 

 with that which we obtain by more easy means. 



Prussian blue is not a simple combination, as has been 

 thought. The following observation will sufficiently prove 

 this assertion : We know, for instance, that the basis of 

 this blue is red oxide : but if this oxide be sufficient of itself 

 for Making Prussian blue, why should not the prussic acid 

 and the red oxide furnish it? Why should not the solutions 

 of this rxide, and the simple alkaline prussiates, giveitalso? 

 T re must necessarily be another element in Prussian blue: 

 the f /.lowing facts clearly demonstrate this : When we 

 apply potash to Prussian blue we obtain a yellow crystal- 



lizablc 



