180 APPENDIX. [No. Vir. 



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 ferrosesquieyanuret 

 is impure till that is removed by alcohol. We have seen also that the 

 change may be effected 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 batteiy a large quantity 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 suitable for long-continued action. 



Table of Decompositions. 

 By Chlorine a/nd Bromine. 



leq. fen-ocyanate) (^^°^ ^ „ ( = 1 eq. red ferro-(5'°'' ^- „ 

 ofpotassa . . = ^^f ^°g^^ ^ cyanate . .Cyanogen 3 



iPotassa 2 •' (Potassium 1. 



i- eq. of chlorine I i eq. chloride of potassium. 



Bromine acts ih the same way. 



By the Gaha/nic Current. 



1 eq. ferrocyanate ) f J'°'^ 

 ofpotassa . .] = S^f ^"f^^ ^„ 



(Potassium 2 



1 eq. of oxygen. 



2 eq. of hydrogen from decomposition 



of water. ( 



= leq.redfen-o.|^°^l- „ 

 cyanate . . Cyanogen 3 



'Potassium Ih 



i eq. of potassa. 



i eq. of hydrogen evolved. 



The action of the acids, &c., has been already sufficiently adverted to. 



Table of Peecipitatbs with the Iodo-feeeoctanate 

 OF Potassa ptjee. 



Grold solution red, no precipitate. 



Platinum .... a little white deposit. 



Mercury, bichloride white, becoming green. 



Lead white, abundant. 



Silver white, with a little reddish tinge. 



Bismuth .... white, afterwards yellow. 



Zinc white. 



Copper dark brown. 



Iron protosalts . . Prussian blue. 



Iron persalts . . . Prussian blue. 



