CYANIDE OF POTASSIUM. 
295v 
ART. XLVII.— ON THE PREPARATION AND USE OF CYA- 
NIDE OF POTASSIUM. By J. Liebig. 
One of the best methods to procure cyanide of potassium 
consists, as is known, in decomposing the ferrocyanide of po- 
tassium at a red heat; but it has many inconveniences, and 
we are constrained to lose a third part of the cyanogen which 
the salt contains. Composed of two atoms of cyanide of po- 
tassium, and one atom of cyanide of iron, no change is pro- 
duced in the former of these combinations by a red heat; but 
the latter is decomposed into carburet of iron with the disen- 
gagement of nitrogen. The carburet of iron formed, absorbs 
the fused cyanide of potassium like a sponge, and we are 
compelled to have recourse to solvents, especially alcohol, to 
obtain the cyanide of potassium free from iron, and without 
loss. 
But, as the cyanide of potassium possesses properties which 
render it a precious means for reduction and separation in 
chemical analysis, I have endeavored to simplify its prepa- 
ration. 
If we dry perfectly (by gentle calcination) on a hot plate 
eight parts of ferrocyanide of potassium, and then mix it inti- 
mately in fine powder with three parts of dry carbonate of 
potassa, and throw the whole together into a red hot Hessian 
crucible, which is to be retained at that temperature, the mix- 
ture fuses into a brown mass, with a rapid disengagement of 
gas; in a few minutes, when the mass has become fluid, and 
has arrived at a red heat, we perceive the depth of the color 
to decrease, and by continuation of the heat to become clear, 
and of an amber yellow; on the introduction of a glass rod, 
the portion adhering when withdrawn, on becoming solid, 
remains at first brown, but becomes yellow; and finally, at 
the end of the operation, the liquid is clear and colorless as 
