K3[W2Cl9] + 16KCN + 2H2O → 2K4[W(CN)8] + 9KCl + H2 + 2KOH
Potassium nonachloridoditungstate(III) react with potassium cyanide and water to produce oktacyanotungstate(IV) potassium, potassium chloride, hydrogen and potassium hydroxide. Potassium cyanide - concentrated solution. The reaction takes place in a boiling solution.