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Potassium hexacyanoferrate(II) | |
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Names: | potassium hexacyanoferrate(II) potassium hexacyanoferroate potassium cyanoferrate potassium ferrocyanide yellow prussiate of potash prussian yellow Е536 food additive |
Formula: | K4[Fe(CN)6] (anhydrous) K4[Fe(CN)6] · 3H2O (trihydrate) |
Molar mass: | 368.345 g/mol (anhydrous) 422.390 g/mol (trihydrate) |
Density: | 1.935 g/cm3 (anhydrous) 1.853 g/cm3 (trihydrate) |
Crystal system: | monoclinic (trihydrate α) a=9.3528 Å, b=16.755 Å, c=9.359 Åα=90°, β=90.076°, γ=90° monoclinic (trihydrate β) a=9.79 Å, b=16.8444 Å, c=9.392 Åα=90°, β=90.069°, γ=90° |
Shapes: |
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Color: | bright-yellow |
Melting point: | ~70 °C"~" is not declared as a valid unit of measurement for this property. (trihydrate) |
Decomposition point: | 650 °C923.15 K <br />1,202 °F <br />1,661.67 °R <br /> (anhydrous) -80.15 °C193 K <br />-112.27 °F <br />347.4 °R <br /> (trihydrate α) |
Refractive index: | 1.577 (trihydrate) |
Magnetic properties: | diamagnetic χ=-1.30 · 10-4cm³/mol |
Stability: | erodes (trihydrate) |
Hardness: | relatively strong (2 on Moh's scale) |
Toxicity: | non-toxic LD50=6400mg/kg |
Description
Inorganic complex compound, salt of alkaline metal potassium and inorganic ferrocyanide acid. From water solutions crystallizes as trihydrate.
Minerals
Occurs in nature as kafehydrocyanite mineral.
Precursors
Reaction between potassium ferricyanide, hydroxide and hydrogen peroxide
Chemical equation:
100.00
g of potassium hexacyanoferrate(II) trihydrate
а 13.28
g of potassium hydroxide, 134.21
g of 3%
peroxide and 77.95
g of potassium ferricyanide is required.Add to the flask with potassium ferricyanide solution hydrogen peroxide and then add small parts of potassium hydroxide with stirring until oxide emission will stop. For purifying compound from hydroxide add large amount of cold ethanol, acetone 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.
Reaction between prussian blue and hydroxide
Chemical equation:
100.00
g of potassium hexacyanoferrate(II) trihydrate
а 53.13
g of potassium hydroxide and 67.81
g of prussian blue is required.Add to flask with prussian blue small amount of water until it will become a thick slurry. Then add small parts of diluted hydroxide solution with intense stirring. Mixture will change color from dark-blue to dark-brown, become more homogeneous and could even boils because of exothermic. Heat it to 100°C for few minutes for reaction completion, filter out a precipitation of iron hydroxide.
Influence of temperature
Growing at higher temperature gives mostly polycrystalline.
Notes
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.
Slowly reacts with diluted sulfuric acid with poisonous hydrocyanic acid emission, so be careful. Concentrated acid decomposes it to carbon monoxide, another ones gives participate of ferrocyanide acid.
Storage conditions
For crystal storing use hermetic vessel with small amount of saturated solution at the bottom or place wadding moistened with such solution. You can use such alternatives as vessel with vaseline or vegetable oil, organic non-hygroscopic solvent (kerosene, benzine or paraffin). Also you can use acrylate polymer or another kinds of solidifying plastic.
Solubility
Temperature | гр/100,00 гр water | гр/100,00 гр ethanol 70% | гр/100,00 гр methanol | гр/100,00 гр formamide | |
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(anhydrous) | (trihydrate) | (anhydrous) | (anhydrous) | (anhydrous) | |
0°C273.15 K <br />32 °F <br />491.67 °R <br /> | 14.3 | ~16.7 | |||
10°C283.15 K <br />50 °F <br />509.67 °R <br /> | 21.1 | 24.8 | |||
20°C293.15 K <br />68 °F <br />527.67 °R <br /> | 28.9 | 33.7 | 0.025 | ||
25°C298.15 K <br />77 °F <br />536.67 °R <br /> | 31.5 | ~37.9 | 14.7 | ||
30°C303.15 K <br />86 °F <br />545.67 °R <br /> | 35.3 | ~42.3 | |||
50°C323.15 K <br />122 °F <br />581.67 °R <br /> | 48.3 | ~59.4 | |||
60°C333.15 K <br />140 °F <br />599.67 °R <br /> | 54.8 | ~67.9 | |||
70°C343.15 K <br />158 °F <br />617.67 °R <br /> | 0.9 | ||||
80°C353.15 K <br />176 °F <br />635.67 °R <br /> | 66.9 | 85 | |||
100°C373.15 K <br />212 °F <br />671.67 °R <br /> | 74.2 | ~95.5 |
Gallery
Sources
Cyanides | |
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Hexacyanoferroates |
Potassium hexacyanoferrate(II) (K4[Fe(CN)6]) • Sodium hexacyanoferrate(II) (Na4[Fe(CN)6]) • Tripotassium-sodium hexacyanoferrate(II) (K3Na[Fe(CN)6]) |
Hexacyanoferriates |
Potassium hexacyanoferrate(III) (K3[Fe(CN)6]) |
Hexacyanocobaltates |
Potassium hexacyanocobaltate(III) (K3[Co(CN)6]) |
Hexacyanochromates |
Potassium hexacyanochromate(III) (K3[Cr(CN)6]) |
Nitroprussides |
Sodium nitroprusside (Na2[Fe(CN)5NO]) |
Complexes |
Cyanocobalamin (C63H88CoN14O14P) |