How do we prepare potassium cyanide from potassium ferrocyanide?
It is something which I am curious about, but cannot find the answer. I am studying inorganic chemistry but this reaction cannot be found.
Answer
Until about 1900, potassium cyanide was produced by melting dry potassium carbonate with dry potassium hexacyanidoferrate(II): $$\ce{K4[Fe(CN)6] + K2CO3 -> 6KCN + FeO + CO2}$$ However, the product contains potassium cyanate, which is approximately formed as follows: $$\ce{K4[Fe(CN)6] + K2CO3 -> 5KCN + KOCN + Fe + CO2}$$
In a small scale, dry potassium hexacyanidoferrate(II) is melted in a covered porcelain crucible. It is heated as long as nitrogen escapes. $$\ce{K4[Fe(CN)6] -> 4KCN + N2 +FeC2}$$ The iron carbide sinks to the bottom and the molten potassium cyanide can be poured off.
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