Potassium ferrocyanide

Small yellow crystals of K₄[Fe(CN)₆]·3H₂O

Potassium ferrocyanide, also known as yellow prussiate of potash or potassium hexacyanoferrate(II), is a coordination compound of formula K₄[Fe(CN)₆]·3H₂O, which forms lemon-yellow monoclinic crystals at room temperature, and which decomposes at its boiling point. It is insoluble in alcohol but a litre of water can dissolve just under three hundred grams of the crystals, and the solution can react with acid to release hydrogen cyanide gas. The resulting hydrogen cyanide (HCN) boils at 26 °C and, being slightly lighter than air, quickly evaporates clear of the release point. Potassium ferrocyanide itself is almost non-toxic.

On February 20, 2002 four Moroccans were arrested while in possession of detailed maps of the United States embassy in Rome, the Rome water supply network, and four kilograms of potassium ferrocyanide.

When combined with ferric salts, potassium ferrocyanide forms the pigment Prussian blue.

See also

• ferrocyanide
• potassium ferricyanide
• Prussian blue

External links

• National Pollutant Inventory - Cyanide compounds fact sheet

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