Potassium ferrocyanide is the inorganic compound with formula K4[Fe(CN)6] · 3H2O. It is the potassium salt of the coordination complex [Fe(CN)6]4−. This salt forms lemon-yellow monoclinic crystals.
It and the related sodium salt are widely used as anticaking agents for both road salt and table salt. The potassium and sodium ferrocyanides are also used in the purification of tin and the separation of copper from molybdenum ores. Potassium ferrocyanide is used in the production of wine and citric acid.