Ferricyanic acid, H₃[Fe(CN)₆]

Hydrogen ferricyanide, Ferricyanic acid, H₃[Fe(CN)₆], maybe obtained as crystalline brown needles by the action of dilute sulphuric acid upon lead ferricyanide and subsequent concentration of the decanted solution. The product is not pure, however. A pure acid is believed to result on decomposition with hydrochloric acid, silver ferricyanide, prepared by the action of silver nitrate on potassium ferricyanide.