Potassium ferrocyanide
| Potassium ferrocyanide trihydrate | |
| Names | |
|---|---|
| IUPAC name
Potassium hexacyanidoferrate(II)
| |
| Other names
Tetrapotassium ferrocyanide, trihydrate; Ferrate (4-), hexacyanido, tetrapotassium, trihydrate[1]
| |
| Identifiers | |
| ECHA InfoCard | 100.034.279 |
| E number | E536 (acidity regulators, ...) |
PubChem CID
|
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CompTox Dashboard (EPA)
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| Properties | |
| C6N6FeK4 | |
| Molar mass | 368.35 g/mol (anhydrous) 422.388 g/mol (trihydrate) |
| Appearance | Light yellow, crystalline granules. |
| Density | 1.85 g/cm3 (trihydrate) |
| Melting point | 69-71°C |
| Boiling point | 400°C (decomp) |
| trihydrate 28.9 g/100 mL (20 °C) | |
| Solubility | insoluble in ethanol, ether |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
|
Potassium ferricyanide |
Other cations
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Sodium ferrocyanide Prussian blue |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Potassium ferrocyanide, also known as potassium prussiate or yellow prussiate of potash or potassium hexacyanidoferrate(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.
Synthesis
Potassium ferrocyanide is the product of the reaction between hydrogen ferrocyanide and potassium hydroxide:
- H4[Fe(CN)6] + KOH → K4[Fe(CN)6]•3H2O[2]
The reaction forms a stable compound that is neither combustible nor pyrophoric.[3] This compound is a strong reducing agent and is thus incompatible with oxidizing agents.[4] Addition of metal chlorates, perchlorates, nitrates, or nitrites to a solution of carefully prepared and otherwise stable potassium ferrocyanide may result in a large explosion.[3]
Properties
Physical characteristics
Although it is insoluble in alcohol, a liter of water can dissolve just under three hundred grams of the crystals, and the solution can react with acid to release toxic 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.
Chemical reactions
When chlorine gas is bubbled through a solution of this compound, potassium ferricyanide is formed in the reaction:
- 2 K4[Fe(CN)6] + Cl2 → 2 K3[Fe(CN)6] + 2 KCl[5]
This reaction can be used to remove potassium ferrocyanide from a solution.[6] When the two are combined, the product is Prussian blue. Potassium ferrocyanide, potassium ferricyanide, and Prussian blue account for over 97% of cyanides in the environment.[7]
Potassium ferrocyanide is also used to test for protein. Acetic acid and K
3Fe(CN)
6 are added to an aqueous solution of the substance being tested. The formation of a white precipitate confirms the presence of protein.[8]
Toxicity
Potassium ferrocyanide itself is only slightly toxic,[3] although adding acid to its aqueous solution releases toxic hydrogen cyanide gas. While it is not mutagenic, it may cause irritation if it is ingested, inhaled, or if it comes into contact with skin.[9] The best solution in these situations is to remove the victim to fresh air or wash the affected area thoroughly with water. It causes harm in aqueous environments and is especially toxic to aquatic organisms. The lethal dose (LD50) in rats is 6400 mg/kg.[3]
Uses
- Naturally, potassium ferrocyanide can be used as an alternate nitrogen source for plants. It is often used as a gardening technique.[10] In an experiment to test this aim, plants were either deprived of nitrogen or given a nitrogen-rich environment while all were exposed to either potassium ferrocyanide or its product, potassium ferricyanide. The plants were unable to sustain themselves solely on the cyanides, but the uptake of the cyanides did increase in the absence of nitrogen. Furthermore, the plants appeared to have different methods for the uptake of the two cyanides.[7]
- Industrially, this complex is used in metal extraction and to make adhesives, computer electronics, fire retardants, cosmetics, dyes, nylon, paints, inks, plexiglass, pharmaceuticals, and rocket propellant.[7] It is also used in low doses in some food preparation. It works as an anti-caking agent and it removes copper from red wine, as copper is used as a fungicide on grapes.[2]
- In the laboratory, potassium ferrocyanide is used to determine the concentration of potassium permanganate, a compound often used in titrations based on redoxreactions.
History
This specific cyanide was part of an alleged terrorist attempt in Italy. On February 21, 2002 four Moroccan Nationalists were arrested with nine pounds of potassium ferrocyanide and a map pinpointing the exact water pipes leading to the United States Embassy in Rome. The presumed plan was that the cyanide would be dumped into the water to poison the Embassy. Whether or not the men were planning an attack, the potassium ferrocyanide mixed with the water would not have been enough to make it toxic. As aforementioned, it is only extremely toxic when mixed with strong acids due to the resulting HCN gas.[10]
See also
References
- ^ "Safety (MSDS) data for potassium ferrocyanide trihydrate". 2006-02-17. Retrieved 2008-02-25.
- ^ a b Wageningen University (2009-02-24). "Food-Info". Retrieved 2009-04-30.
- ^ a b c d JT Baker, Inc. (2006-02-13). "Potassium ferrocyanide MSDS". Retrieved 2009-04-30.
- ^ Edwin J. deBeer, Axel M. Hjort (1935-03). "Employment of Potassium Ferrocyanide in Standardization of Dilute Potassium Permanganate". Retrieved 2009-04-30.
{{cite web}}: Check date values in:|date=(help) - ^ NIH. "Summary of Data for Chemical Selection" (PDF). Retrieved 2009-04-30.
- ^ Barbara M. Ferrier, Derek Jarvis, and Vincent Du Vigneaud (1965-11). "Deamino-oxytocin. Its Isolation by Partition Chromatography on Sephadex and Crystallization from Water, and its Biological Activities". Retrieved 2009-04-30.
{{cite web}}: Check date values in:|date=(help)CS1 maint: multiple names: authors list (link) - ^ a b c Yu XZ, Gu JD, Li TP (2008). "Availability of ferrocyanide and ferricyanide complexes as a nitrogen source to cyanogenic plants". Archives of Environmental Contamination and Toxicology. 55 (2): 229–37. doi:10.1007/s00244-007-9101-6. PMID 18180862.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Sherman, Henry Clapp (2007). Methods of Organic Analysis. READ BOOKS. p. 313. ISBN 1408628023.
- ^ Nishioka H (1975). "Mutagenic activities of metal compounds in bacteria". Mutation Research. 31 (3): 185–9. PMID 805366.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ a b Melinda Henneberger (2002-02-21). "A NATION CHALLENGED: SUSPECTS; 4 Arrested in Plot Against U.S. Embassy in Rome". The New York Times. Retrieved 2009-04-30.