Potassium ferrocyanide

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Potassium ferrocyanide

IUPAC name	Potassium hexacyanoferrate(II)
Other names	Tetrapotassium ferrocyanide, trihydrate; Ferrate (4-), hexacyano, tetrapotassium, trihydrate^[1]
Identifiers
CAS number	[13943-58-3 (anhydrous product); 14459-95-1 (trihydrate)]
Properties
Molecular formula	C₆N₆FeK₄
Molar mass	422.39 g/mol (trihydrate)
Appearance	Yellow, crystalline granules.
Density	1.85 g/cm³, solid
Melting point	(? K)
Boiling point	decomposes
Solubility in water	28.9 g/100 mL (water, 20° C)
Related compounds
Other anions	Potassium ferricyanide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

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 (HCN) gas. The resulting HCN gas boils at 26 °C and, being lighter than air (with a gaseous density of 0.94), quickly evaporates clear of the release point. Potassium ferrocyanide itself is only slightly toxic.^[2]

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

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