K4[Fe(CN)6] is a chemical compound known as potassium ferrocyanide. It consists of four potassium ions (K+) and one ferrocyanide ion ([Fe(CN)6]4-). The ferrocyanide ion contains a central iron (Fe) atom surrounded by six cyanide (CN) groups, which are coordinated to the iron. This compound is often used in various applications, including as a food additive, in photography, and in the production of blue pigments like Prussian blue. It is generally considered safe in small amounts, but caution is advised due to the toxicity of cyanide in larger quantities.