Potassium hexacyanoferrate(III)

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   Potassium hexacyanoferrate(III)   
Names: potassium hexacyanoferrate(III)
potassium hexacyanoferriate
potassium cyanoferrite
potassium ferricyanide
red prussiate of potash
prussian red

Formula: K3[Fe(CN)6]
SMILES: [C-]#N.[C-]#N.[C-]#N.[C-]#N.[C-]#N.[C-]#N.[K+].[K+].[K+].[Fe+3]
Molar mass: 329.247 g/mol
Density: 1.845 g/cm3
Crystal system: monoclinic (α)
a=7.058 Å, b=10.426 Å, c=8.401 Åα=90°, β=107.311°, γ=90°
monoclinic (β)
a=14.021 Å, b=10.401 Å, c=8.339 Åα=90°, β=107.21°, γ=90°
orthorhombic (γ)
a=13.4226 Å, b=10.3964 Å, c=8.3814 Åα=90°, β=90°, γ=90°

Color: dark-red
Melting point: 300 °C573.15 K <br />572 °F <br />1,031.67 °R <br />
Decomposition point: -173.15 °C100 K <br />-279.67 °F <br />180 °R <br /> (α)
Refractive index: 1.573
Magnetic properties: paramagnetic
χ=2.29 · 10-4cm³/mol
Hardness: relatively strong
Toxicity: non-toxic


Inorganic complex compound, salt of alkaline metal potassium and inorganic ferricyanide acid. Doesn't form water hydrates.


Reaction between potassium ferrocyanide, hydrogen peroxide and sulfuric or hydrochloric acid

Chemical equation:

2K4[Fe(CN)6] + H2O2 + H2SO4 = 2K3[Fe(CN)6] + K2SO4 + 2H2O
2K4[Fe(CN)6] + H2O2 + 2HCl = 2K3[Fe(CN)6] + 2KCl + 2H2O

For preparation of 100.00g of potassium hexacyanoferrate(III) а 128.29g of potassium ferrocyanide trihydrate, 172.18g of 3% peroxide and 40.25g of 37% sulfuric or 29.93g of 37% hydrochloric acid is required.
Add to the flask with potassium ferrocyanide solution hydrogen peroxide and then add small parts of acid with stirring until a precipitation forming will stop. For purifying compound from potassium salts add large amount of cold ethanol, isopropanol or toluene to solution, salt will settle to the bottom in the form of fine crystals or powder. Filter precipitate and wash it with small amount of the same solvent, then filter the solution and use it for crystal growing.

Influence of temperature

While temperature increasing or decreasing rapidly, strokes could be formed at crystal faces.
Growing at higher temperature gives mostly polycrystalline.

Influence of impurities

Opacity of crystals is increasing with compound impurity.


At sunlight and air oxygen solution decomposes with forming green precipitate which impairs growth. So make as saturated solution as possible and do not use if for growth for a long time-every next crystallization layer will become more dirty and deformed.
Reacts with acids with hydrocyanic acid emission.

Storage conditions

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.


Temperatureгр/100,00 гр waterгр/100,00 гр methanolгр/100,00 гр hydrazineгр/100,00 гр dimethylformamideгр/100,00 гр formamide
0°C273.15 K <br />32 °F <br />491.67 °R <br />29.9
10°C283.15 K <br />50 °F <br />509.67 °R <br />38.3
15°C288.15 K <br />59 °F <br />518.67 °R <br />~42.4
20°C293.15 K <br />68 °F <br />527.67 °R <br />46.42
25°C298.15 K <br />77 °F <br />536.67 °R <br />
30°C303.15 K <br />86 °F <br />545.67 °R <br />52.7
40°C313.15 K <br />104 °F <br />563.67 °R <br />59.5
50°C323.15 K <br />122 °F <br />581.67 °R <br />~65.2
60°C333.15 K <br />140 °F <br />599.67 °R <br />70.9
70°C343.15 K <br />158 °F <br />617.67 °R <br />77.50.31
80°C353.15 K <br />176 °F <br />635.67 °R <br />81.8
90°C363.15 K <br />194 °F <br />653.67 °R <br />~86.7
100°C373.15 K <br />212 °F <br />671.67 °R <br />91.6
Insoluble in ethanol, acetone, diethyl ether, toluene, aniline, pyridine, ethyl acetate and isopropanol.