Potassium Ferrocyanide: Formula, Properties, Risks and Uses

He Potassium ferrocyanide , Also known as Prussian potassium or yellow hexacyanoferrate (II), is an inorganic compound of formula K 4 [Fe (CN) 6 ].

The compound is a potassium salt of the ferrocyanide coordination complex (Fe (CN) 6 4- ) And is generally found in the trihydrate form K 4 [Fe (CN) 6 ] · H 2 O. Its structure is shown in figure 1 (EMBL-EBI, 2008).

Formula and chemical structure of potassium ferrocyanide. Figure 1: structure of potassium ferrocyanide.

Historically, the compound was made from organically obtained nitrogenous carbon sources, iron filings and potassium carbonate. Common Sources of nitrogen And carbon were scraps of leather, offal or dried blood.

Currently potassium ferrocyanide is industrially produced from hydrogen cyanide, ferrous chloride and calcium hydroxide, the combination of which gives Ca 2 [Fe (CN) 6 ] · 11H 2 OR.

This solution is then treated with potassium salts to precipitate the calcium salt of CaK 2 [Fe (CN) 6 ], Which in turn is treated with potassium carbonate to give the tetrapotassium salt.

Physical and chemical properties

Potassium ferrocyanide is a pale yellow or pale yellow monoclinic crystal, depending on the level of hydration, without a characteristic aroma (National Center for Biotechnology Information, 2017). Its appearance is shown in figure 2 (Potassium ferrocyanide, 2017).

Potassium Ferrocyanide: Formula, Properties, Risks and Uses

The compound has a molecular weight of 368.35 g / mol for the anhydrous form and 422.388 g / mol for the trihydrate form. It has a density of 1.85 g / ml and a melting point of 70 ° C where it begins to decompose (Royal Society of Chemistry, 2015).

The compound is soluble in water, it being possible to dissolve 28.9 grams of compound in 100 ml of this solvent. It is insoluble in diethyl ether, ethanol and toluene. The compound reacts to heat to form potassium cyanide according to the reaction:

K 4 [Fe (CN) 6 ] → 4 KCN + FeC 2 + N 2

In combination with concentrated acids, it forms hydrogen cyanide (HCN) which is a flammable, highly poisonous gas and can form explosive mixtures in the air (Laffort, 2001).

Reactivity and hazards

Potassium ferrocyanide is a stable compound, incompatible with oxidizing agents and strong acids. Potassium ferrocyanide is non-toxic and does not decompose into cyanide in the body. Toxicity in rats is low, with lethal dose (LD50) at 6400 mg / kg.

The substance is toxic to the lungs and mucous membranes. The compound can cause irritation in case of contact with skin and eyes.

Ingestion may cause irritation of the gastrointestinal tract and in case of inhalation it causes irritation of the nasal mucosa and respiratory system.

Contact with eyes may result in corneal damage or blindness. Contact with skin may cause swelling and blisters.

Inhalation of dust will produce irritation of the gastrointestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe overexposure may result in lung damage, asphyxia, unconsciousness, or death.

Eye contact

In case of contact with the eyes, the contact lenses should be checked and removed. Immediately flush eyes with plenty of cool water for at least 15 minutes.

Skin contact

Immediately flush affected area with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Cover irritated skin with an emollient.

Wash clothing and shoes before reuse. If the contact is severe, wash with a disinfectant soap and cover the skin contaminated with an anti-bacterial cream


The victim should be moved to a cool place. If it does not breathe, artificial respiration should be given. If breathing is difficult, give oxygen.


If the compound is ingested, do not induce vomiting unless directed to do so by medical personnel. Loosen tight clothing such as a shirt collar, belt or tie.

In all cases, medical attention should be obtained immediately (Material Safety Data Sheet Potassium ferrocyanide trihydrate, 2013).


1- Food industry

Prussian yellow is also known for its European approved food additive number: E536 and has various uses in the food industry. It is used as anti-caking agent for both road salt and table salt.

It also has an oenological use to eliminate copper and iron in winemaking. Copper is used as fungicide in grapes (Wageningen University, 2014).

It is also used for the fermentation of citric acid (D. Clark, 1965). Potassium ferrocyanide can also be used as a fertilizer for plants.

2- Mining and metallurgy industry

Potassium ferrocyanide is used to remove copper from molybdenum minerals. It is also used for the cementation of steel (Potassium ferrocyanide, K4Fe (CN) 6, 2012).

Cementation is a thermochemical treatment applied to steel parts. The process contributes carbon to the surface by diffusion, which is impregnated by modifying its composition.

3- Laboratory reagent

Potassium ferrocyanide is used to determine the concentration of potassium permanganate, a compound often used in titrations based on redox reactions.

Potassium ferrocyanide is used in a mixture with potassium ferricyanide and phosphate buffered solution to provide a buffer for beta-galactosidase, which is used to cleave X-Gal (5-bromo-4-chloro-3-indolyl-β -D-galactopyranoside, giving a bright blue display where an antibody (or another molecule), conjugated to Beta-gal, has attached itself to its target.

The compound is also used for the production of Prussian blue. Reacting with Fe (III) gives a Prussian blue color, so it is used as an identification reagent for iron in laboratories.

It is also used for the determination of zinc in samples of zinc sulphide. Dissolve the sample in HCl 6 N And boiled under hood to remove hydrogen sulfide, neutralized with ammonium hydroxide and 3 drops of HCl added.

Heat to boiling and add 5 ml of solution 1 N Of potassium ferrocyanide. The presence of a white precipitate of zinc ferrocyanide indicates a positive test for this element (Mehlig, 1927).


  1. S. Clark, K. I. (1965). Effect of potassium ferrocyanide on the chemical composition of molasses mash used in the citric acid fermentation. Biotechnology and bioengineering Volume 7, Issue 2 , 269-278. Retrieved from onlinelibrary.wiley.com.
  2. EMBL-EBI. (2008, January 16). Potassium hexacyanoferrate (4-) . Retrieved from ebi.ac.uk.
  3. (2001, March 5). POTASSIUM FERROCYANURE. Recovered from laffort.com.
  4. Material Safety Data Sheet Potassium ferrocyanide trihydrate. (2013, May 21). Retrieved from sciencelab.com.
  5. Mehlig, J.P. (1927). Use of potassium ferrocyanide as a confirmatory test for zinc. Chem. Educ. 4 (6) , 722. Retrieved from pubs.acs.org.
  6. National Center for Biotechnology Information. . (2017, April 15). PubChem Compound Database; CID = 161067 . Retrieved from pubchem.ncbi.nlm.nih.gov.
  7. Potassium ferrocyanide . (2017, March 25). Retrieved from sciencemadness.org.
  8. Potassium ferrocyanide, K4Fe (CN) 6 . (2012). Retrieved from atomistry.com.
  9. Royal Society of Chemistry. (2015). Potassium ferrocyanide . Recovered from chemspider.com.
  10. Wageningen University. (2014, August 14). E536: Potassium ferrocyanide. Retrieved from food-info.net.

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