K3CrCN6

Potassium hexacyanoferrate(III), with the chemical formula K3[Fe(CN)6], is an inorganic coordination compound. It is also known as potassium ferricyanide. The compound consists of potassium cations (K+) and the hexacyanoferrate(III) anion ([Fe(CN)6]3-). In the anion, a central iron atom is in the +3 oxidation state, coordinated to six cyanide ligands (CN-).

Potassium hexacyanoferrate(III) typically appears as bright red crystals. It is soluble in water, forming a yellow-orange solution. The compound is a strong oxidizing agent. It reacts with ferrous ions (Fe2+) to form Turnbull's blue, a deep blue precipitate. This reaction is historically significant and was used as a test for ferrous ions.

K3[Fe(CN)6] has various applications. It is used in photography as a bleaching agent in color processing and for toning prints. In analytical chemistry, it serves as an oxidizing titrant. It is also employed in blueprinting and as a component in some electrochemical applications. The compound is considered moderately toxic due to the potential release of cyanide ions under certain conditions, such as strong acidic environments.