Sodium ferrocyanide

Sodium ferrocyanide is the sodium salt of the coordination compound of formula [Fe(CN)6]4−. In its hydrous form, Na4Fe(CN)6 · 10 H2O (sodium ferrocyanide decahydrate), it is sometimes known as yellow prussiate of soda. It is a yellow crystalline solid that is soluble in water and insoluble in alcohol. The yellow color is the color of ferrocyanide anion. Despite the presence of the cyanide ligands, sodium ferrocyanide has low toxicity (acceptable daily intake 0–0.025 mg/kg body weight[2]). The ferrocyanides are less toxic than many salts of cyanide, because they tend not to release free cyanide.[3] However, like all ferrocyanide salt solutions, addition of an acid or exposure to UV light can result in the production of hydrogen cyanide gas, which is extremely toxic. [4][5]

Sodium ferrocyanide[1]
Names
IUPAC name
Tetrasodium [hexacyanoferrate(II)]
Other names
Yellow prussiate of soda (YPS), Tetrasodium hexacyanoferrate, Gelbnatron, Ferrocyannatrium, sodium hexacyanoferrate(II), Yellow blood salt
Identifiers
3D model (JSmol)
ECHA InfoCard 100.033.696
EC Number
  • 237-081-9
E number E535 (acidity regulators, ...)
UNII
  • InChI=1S/6CN.Fe.4Na/c6*1-2;;;;;/q6*-1;+2;4*+1
  • [Na+].[Na+].N#C[Fe-4](C#N)(C#N)(C#N)(C#N)C#N.[Na+].[Na+]
Properties
Na4[Fe(CN)6]
Molar mass 303.91 g/mol
Appearance pale yellow crystals
Odor odorless
Density 1.458 g/cm3
Melting point 435 °C (815 °F; 708 K) (anhydrous)
81.5 °C (178.7 °F; 354.6 K) (decahydrate) (decomposes)
10.2 g/100 mL (10 °C)
17.6 g/100 mL (20 °C)
39.7 g/100 mL (96.6 °C)
1.530
Structure
monoclinic
Related compounds
Other anions
 Sodium ferricyanide (Red prussiate of soda)
Other cations
 Potassium ferrocyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Uses

When combined with an Fe(III) salt, it converts to a deep blue pigment called Prussian blue, FeIII
4[FeII
(CN)
6]
3.[6] It is used as a stabilizer for the coating on welding rods. In the petroleum industry, it is used for removal of mercaptans.

In the EU, ferrocyanides (E 535–538) were, as of 2018, solely authorized as additives in salt and salt substitutes, where they serve as anticaking agents. The kidneys are the organ susceptible to ferrocyanide toxicity, but according to the EFSA, ferrocyanides are of no safety concern at the levels at which they are used.[7]

Production

Sodium ferrocyanide is produced industrially from hydrogen cyanide, ferrous chloride, and calcium hydroxide, the combination of which affords Ca2[Fe(CN)6] · 11 H2O. A solution of this salt is then treated with sodium salts to precipitate the mixed calcium-sodium salt CaNa2[Fe(CN)6]2, which in turn is treated with sodium carbonate to give the tetrasodium salt.[8]

References
  1. Sodium ferrocyanide MSDS Archived 2010-05-17 at the Wayback Machine
  2. "Toxicological evaluation of some food additives including anticaking agents, antimicrobials, antioxidants, emulsifiers and thickening agents". inchem.org. World Health Organization. 1974. Archived from the original on 1 December 2010. Retrieved 18 May 2009.
  3. Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
  4. "PubChem Compound Summary for CID 26129, Sodium ferrocyanide". National Center for Biotechnology Information. PubChem. Archived from the original on 2023-02-13. Retrieved 2023-01-17.
  5. "PubChem Compound Summary for CID 768, Hydrogen Cyanide". National Center for Biotechnology Information. PubChem. Archived from the original on 2023-03-03. Retrieved 2023-01-17.
  6. "Prussian blue". Encyclopædia Britannica. Archived from the original on 5 September 2015. Retrieved 18 May 2009.
  7. Peter Aggett, Fernando Aguilar, Riccardo Crebelli, Birgit Dusemund, Metka Filipič, Maria Jose Frutos, Pierre Galtier, David Gott, Ursula Gundert‐Remy, Gunter Georg Kuhnle, Claude Lambré, Jean‐Charles Leblanc, Inger Therese Lillegaard, Peter Moldeus, Alicja Mortensen, Agneta Oskarsson, Ivan Stankovic, Ine Waalkens‐Berendsen, Rudolf Antonius Woutersen, Matthew Wright and Maged Younes. (2018). "Re‐evaluation of sodium ferrocyanide (E 535), potassium ferrocyanide (E 536) and calcium ferrocyanide (E 538) as food additives". EFSA Journal. 16 (7): 5374. doi:10.2903/j.efsa.2018.5374. PMC 7009536. PMID 32626000.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. Gail, E.; Gos, S.; Kulzer, R.; Lorösch, J.; Rubo, A.; Sauer, M.; Kellens, R.; Reddy, J.; Steier, N. (2011). "Cyano Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_159.pub3.
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