Prussian blue

Prussian blue is a deep-blue iron hexacyanoferrate compound used as a pigment and as an oral medicine that binds certain radioactive or toxic substances in the gut.

Iron hexacyanoferrate: A family of coordination compounds built from iron ions and hexacyanoferrate units. Prussian blue is a mixed-valence member of this compound family.
Prussian blue staining: A histochemical method that detects ferric iron in tissue using formation of a blue iron cyanide pigment. The pigment’s formation makes it useful for locating stored iron in biological samples.
Johann Jacob Diesbach: An early eighteenth-century Berlin pigment maker associated with the discovery of Prussian blue. Diesbach is traditionally credited with producing the pigment while attempting to make red lake.
Ultramarine: A vivid blue pigment historically made from lapis lazuli and later produced synthetically. Unlike costly natural ultramarine, Prussian blue was an early affordable synthetic blue.
Intervalence charge transfer: An optical process in which an electron transfers between metal ions in different oxidation states. Electron transfer between iron sites produces Prussian blue’s strong blue absorption.
Radiogardase: A pharmaceutical formulation of insoluble Prussian blue used to treat internal contamination by radioactive cesium or thallium. This is the medical product used when Prussian blue is prescribed for decorporation.
Johann Konrad Dippel: A German alchemist and physician whose preparations are linked to the early production of Prussian blue. Accounts of the discovery connect Diesbach’s failed recipe to materials supplied by Dippel.
Cobalt blue: A stable blue pigment consisting mainly of cobalt aluminate. Cobalt blue is a mineral-based oxide pigment, unlike Prussian blue’s iron–cyanide lattice.
Cesium-137: A radioactive cesium isotope produced by nuclear fission, with a half-life of about 30 years. Prussian blue binds cesium ions in the gut, reducing their reabsorption.
Cyanotype: A photographic printing process that forms blue images using light-sensitive iron compounds. Cyanotype uses iron chemistry to create a blue image, though not Prussian blue as its principal image-forming pigment.

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