Potassium ferrocyanide is a yellow crystalline compound, designated E536, used as an anticaking agent in table salt and a clarifying agent in winemaking. In salt, tiny amounts keep the crystals free-flowing in humid conditions; in wine, it removes excess iron and copper that cause hazes and off-flavours, precipitating as filterable complexes. The name alarms consumers, since it contains the word “cyanide,” but the cyanide groups are tightly bound to iron in a stable complex that does not release toxic cyanide under food conditions, and toxicological reviews support its safety at permitted levels. It must be declared on labels where used directly. The compound’s persistence in approved additive lists despite its forbidding name shows regulators judging chemistry rather than nomenclature, though clean-label pressures have reduced its use in some markets.