

History of prussiates. 97 



new solution of oxide, which takes the place of the ferrtf- 



ginous carbonate, decomposes the prussiate of potash, as 



any solution of iron would do.* 



When Prussian lixivium therefore is employed instead of Inaccuracy of 



a crystallized prussiate in an analysis, we add to the pro- ^ c ? russian 

 ■ . 1 lixivium as a 



duct in. the first place red oxide, which made part of the test, 



ferruginous carbonate; and in the next black oxide, which 



is a constant element of the triple prussiate contained in the 



lixivium. 



Chemists very soon discovered the faults of these lixivi- 

 ums, though they were not at first aware, that they con- 

 tained two very different combinations of iron, the carbon- 

 ate of which 1 am speaking, and the triple prussiate. Many, Attempts to 

 on seeing the blue they yielded with acids, even thought this conecl lU 

 blue existeeun them as a distinct substance ; and endeavoured 

 to precipitate it, whether it were Prussian blue or oxide, 

 not affecting the alkaline prussiate, which they sup- 

 posed to possess the tinging property without being in- 

 debted for it to iron. From their attempts arose the receipts 

 for precipitated lixiviums, which occur in every work on 

 chemistry. But since the inquiries of Scheele and Berthol- 

 let, it has been found, that these receipts answer the end 

 but imperfectly; for it is easy to see, that it was not suffi- 

 cient to free a lixivium from the oxide introduced into it by 

 the carbonate j there remained farther to be guarded against 

 the black oxide, which belongs to the triple prussiate, and 

 the existence of which was the less suspected, because the 

 addition of acids, without the intervention of light or heat, 

 could not render the products of its decomposition percep- 

 tible. 



I shall not stop to analyse the phenomena, that presented 

 themselves during the preparation of lixivia either hot or 

 cold, because, as the inutility of prussiates for the evalu- 

 ation of iron in analyses is now well knoAvn, the particu- 

 lars would not be very interesting. In the same manner I Other prussi- 

 shall pass over the proposed test liquors with ammonia, lime, ^ w'iSou* 1 " 

 magnesia, &c. because they arc themselves triple prussiates, counterproof. 



* It is the mixture of these same salts, which enables the mother- Prussian bine 



waters of soda to alloid Prussian blue by the addition of an acid. from mother 



water of soda. 



on 



