Scientific name: ferric ferrocynanide
aka: Prussian blue
- UVA and UVB protecting
- sun protection
Ferric Ferrocyanide (CI 77510): an inorganic mineral salt used to provide a rich blue color. Cosmetic-grade ferric ferrocyanide is approved for use on the eyes and face in the U.S., and on lips, eyes and face in the E.U. and Japan. Please note: Ferric ferrocyanide is not approved for use on the lips in the U.S.
Prussian blue was one of the first synthetic pigments. It is employed as a very fine colloidal dispersion, as the compound itself is not soluble in water. It is famously complex, owing to the presence of variable amounts of other ions and the sensitive dependence of its appearance on the size of the colloidal particles formed when it is made. The pigment is used in paints, and it is the traditional "blue" in blueprints.
In medicine, Prussian blue is used as an antidote for certain kinds of heavy metal poisoning, e.g., by cesium and thallium. In particular it was used to absorb 137Cs+ from those poisoned in the Goiânia accident. Prussian Blue is orally administered. The therapy exploits Prussian Blue's ion exchange properties and high affinity for certain "soft" metal cations.
Prussian blue lent its name to prussic acid (hydrogen cyanide), which was derived from it. In Germany, hydrogen cyanide is called Blausäure ("blue acid"), and Joseph Louis Gay-Lussac gave cyanide its name, from the Greek word κυανός (kyanos, "blue"), because of the color of Prussian blue.
Despite the fact that it is prepared from cyanide salts, Prussian blue is nontoxic because the cyanide groups are tightly bound to Fe. Other polymeric cyanometalates are similarly stable with low toxicity.
Prussian blue is a microcrystalline blue powder. It is insoluble, but the crystallites tend to form a colloid. Such colloids can pass through fine filters. Despite being one of the oldest known synthetic compounds, the composition of Prussian blue remained uncertain for many years.
Vincent van Gogh's Starry Night uses Prussian and Cerulean blue pigments.
see also: Pigment