Potassium ferrocyanide

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Not to be confused with potassium ferricyanide.
Potassium ferrocyanide
Potassium ferrocyanide aka potassium hexacyanidoferrate(II).jpg
Potassium ferrocyanide sample
IMG 0617.JPG
K4[Fe(CN)6]•3H2O crystals, grown by following ChemPlayer's method of converting K3Fe(CN)6 to the ferrocyanide salt
IUPAC name
Potassium hexacyanidoferrate(II)
Other names
Ferrate hexacyano tetrapotassium trihydrate
Potassium hexacyanoferrate (II) trihydrate
Tetrapotassium ferrocyanide trihydrate
Yellow prussiate of potash
Molar mass 368.35 g/mol (anhydrous)
422.388 g/mol (trihydrate)
Appearance Light yellow solid
Odor Odorless
Density 1.85 g/cm3 (trihydrate)
Melting point 70 °C (158 °F; 343 K) (decomposes)
Boiling point Decomposes
28.9 g/100 ml (20 °C)
Solubility Insoluble in diethyl ether, ethanol, toluene
Vapor pressure ~0 mmHg
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
6400 mg/kg (oral, rat)
Related compounds
Related compounds
Prussian blue
Potassium ferricyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium ferrocyanide or potassium hexacyanidoferrate(II) is is the potassium salt of the ferrocyanide coordination complex. It's generally available as trihydrate, K4[Fe(CN)6]·3 H2O.



Pyrolysis of potassium ferrocyanide will yield potassium cyanide:

K4[Fe(CN)6] → 4 KCN + FeC2 + N2

Adding ferric chloride to a solution of this compound will yield Prussian blue.

Treatment of potassium ferrocyanide with nitric acid gives H2[Fe(NO)(CN)5]. After neutralization of this intermediate with sodium carbonate, red crystals of sodium nitroprusside can be selectively crystallized.


Potassium ferrocyanide is a lemon yellow solid, soluble in water, but less so in organic solvents.


Potassium ferrocyanide can be purchased online. It can also be bought from eBay and Amazon.


Potassium ferrocyanide is produced industrially from hydrogen cyanide, ferrous chloride, and calcium hydroxide, the combination of which affords Ca2[Fe(CN)6]·11H2O. This solution is then treated with potassium salts to precipitate the mixed calcium-potassium salt CaK2[Fe(CN)6], which in turn is treated with potassium carbonate to give the tetrapotassium salt.

Can be prepared by heating a nitrogen source, such as potassium nitrate, with iron and carbon. The product is purified via recrystallization from water.




Potassium ferrocyanide is irritant and should he handled with care.

While its molecule contains cyanide groups, potassium ferrocyanide cannot be broken down to hydrogen cyanide in the organism, making it nontoxic.


Potassium ferrocyanide should be stored in closed bottles, away from strong acidic vapors.


No special disposal is required. Can be dumped in trash.


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