potassium ferricyanide CAS#13746-66-2

Red prussiate (IUPAC name Potassium hexacyanoferrate(III), also known as red prussiate of Potash, Prussian red, and potassium ferricyanide) occurs as bright red crystals which are soluble in water. Potassium ferricyanide is manufactured by passing chlorine into a solution of potassium ferrocyanide. It is not considered to be toxic but is dangerous when heated or mixed with other chemicals.
Potassium ferricyanide is used to prepare Prussian Blue, the deep blue pigment in blue printing. It is used for the testing for ferrous ions. Potassium ferricyanide is widely used as an oxidizing agent in photographic processing to remove silver from negatives and positives, a process called dot etching.  In color photograph, potassium ferricyanide is used to reduce the size of color dots without reducing their number, as a kind of manual color correction. Potassium ferricyanide is often used in physiological experiments as a means of increasing a solutions redox potential (Eo 436 mV at pH 7). Potassium ferricyanide is applied to harden iron and steel, in electroplating, dyeing wool and as a laboratory reagent. It is a mild oxidizing agent used in organic synthesis. It is associated with potassium hydroxide solution used to formulate Murakami‘s etchant, which is useful for metallographers to provide contrast between binder and carbide phases in cemented carbides. Further, it is used in many amperometric biosensors as an electron transfer agent replacing an enzyme's natural electron transfer agent such as oxygen with the enzyme glucose oxidase. It is an active ingredient in blood glucose meters used by diabetics. Potassium ferricyanide can be used as chromogenic reagent for the determination of captopril, the first orally active angiotensin converting enzyme inhibitor, which is applied for the treatment of hypertension, coronary heart disease and congestive heart failure in clinical medicine.