200 Mr. Smee on the Ferrosesquicyanuret of Potassium. 



find iron in everything he examines. With excess of alkali, 

 on the contrary, no precipitate of Prussian blue is produced; 

 and therefore if search be made for that most useful of all 

 metals, the experiment would declare that iron had no real 

 existence; but if the golden mean be employed, or the solution 

 be but very slightly acid, the ferrosesquicyanuret, as well as 

 the ferrocyanuret, become most valuable and delicate tests, 

 the one for the peroxide, the other for the protoxide of that 

 metal. 



The change by chlorine and bromine has been shown to 

 result from the abstraction of the half equivalent of potassium 

 by the formation of chloride or bromide of that metal, and 

 therefore the ferrosesquicyanuret is impure till that is removed 

 by alcohol. We have seen also that the change may be ef- 

 fected by the iodic, nitric, and chloric acids, but by these 

 methods the salt is also contaminated to a great extent by the 

 nitrate of potash, but to a much less extent with the chlorate, 

 and scarcely at all with the iodate ; with phosphorus the salt 

 in a very impure state may still be made. With peroxide of 

 manganese, however, and the galvanic current, it may be made 

 of absolute purity. 



This last mode will probably supersede entirely every other 

 mode of preparation, as with a galvanic battery a large quan- 

 tity can be readily made. The battery which I have used 

 for these experiments is the platinized silver, which from its 

 simplicity is so well adapted for general purposes, and suit- 

 able for long-continued action. 



Bank of England, 

 Feb. 12, 1840. 



Table of Decompositions. 

 By Chlorine and Bromine. 



["Iron 1 

 1 eq. Ferrocyanate \ I Cyanogen 3 



p 

 of Potassa/ I Potassa 2 )= 1 eq. Red fer-* 



Iron 1. 

 Cyanogen 3. 



2 equivalent of chlorine J 5 equivalent chloride of potassium. 



Bromine acts in the same way. 



By the Galvanic Current. 



1 eq. Ferrocyanate "1 J / ori o J 1 eq. Red 



"ofPoi =)i^a"S|= < |F-roc ) ,na t e \ 



eq. of Oxygen. J eq. of Potassa. 



\ eq. of Hydrogen from decomposition |_ e q- f Hydrogen evolved, 

 of water. 



The action of the acids, &c. have been already sufficiently 



adverted to. 



