2CuSO4 + 4KCN → 2CuCN + C2N2 + 2K2SO4
or
2CuSO4 + 4KCN → 2CuCN + (CN)2 + 2K2SO4[3,16]
Copper sulfate react with potassium cyanide to produce copper(I) cyanide, cyanogen and potassium sulfate. Potassium cyanide - diluted solution. The reaction takes place in a boiling solution.