Question

How to prepare cyanide from potassium ferri cyanide?

Answer 1

up vote
7
down vote
accepted
Until about 1900, potassium cyanide was produced by melting dry potassium carbonate with dry potassium hexacyanidoferrate(II):
K4[Fe(CN)6]+K2CO3⟶6KCN+FeO+CO2
KX4[Fe(CN)X6]+KX2COX3⟶6KCN+FeO+COX2
However, the product contains potassium cyanate, which is approximately formed as follows:
K4[Fe(CN)6]+K2CO3⟶5KCN+KOCN+Fe+CO2
KX4[Fe(CN)X6]+KX2COX3⟶5KCN+KOCN+Fe+COX2
In a small scale, dry potassium hexacyanidoferrate(II) is melted in a covered porcelain crucible. It is heated as long as nitrogen escapes.
K4[Fe(CN)6]⟶4KCN+N2+FeC2
KX4[Fe(CN)X6]⟶4KCN+NX2+FeCX2
The iron carbide sinks to the bottom and the molten potassium cyanide can be poured off.