254 DEOXIDATION OF FERRTDCYANIDE OF POTASSIUM, 
liquid. The occurrence of these blue streaks is a fact 
which deserves particular attention, since it appears to 
prove that the body resembling prussian blue is able to 
form at places in the solution of the ferridcyanide where 
there is no metallic iron. 
If metallic iron be left sufficiently long in contact with 
the solution of ferridcyanide of potassium, the latter be- 
comes almost entirely decolorized, and moreover loses the 
property of forming prussian blue on bright iron. Such a 
solution affords with pernitrate of iron considerable dark 
blue precipitates ; with the protosulphate of iron, on the 
contrary, white ones. 
Metallic zinc decomposes the solution of ferridcyanide no 
less rapidly than the iron. If bright lamina? of zinc be placed 
in an open vessel filled with this solution, yellowish-white 
points soon appear on them, and after some time a dirty 
white substance is deposited in the state of a powder at the 
bottom of the vessel. It consists, according to preliminary 
experiments, of the cyanide of potassium and zinc, which 
is probably mixed with some oxide of zinc. If only a trace 
of this white body be formed, the residuous solution of fer- 
ridcyanide is rendered blue by the nitrate of the peroxide 
of iron, and the precipitate of prussian blue is more abund- 
ant when the action of the zinc on the solution of the fer- 
ridcyanide has continued for some length of time. The so- 
ution, altered in this manner, is also no longer capable of 
producing prussian blue on bright iron. It is also a very 
remarkable circumstance that the solution thus altered by 
zinc disengages ammonia in perceptible quantity when hy- 
drate of potash is added to it, and it is then warmed. In 
order that the above changes may be effected in the solu- 
tion of the ferridcyanide of potassium by the zinc, it like- 
wise appears necessary that free oxygen should be pre- 
sent. 
When a solution of the ferridcyanide of potassium is 
brought into contact with arsenic, antimony, bismuth, lead 
