PRODUCTS

PRUSSIAN RED

Prussian red is the chemical compound with the formula K₃[Fe(CN)₆], containing the octahedrally coordinated [Fe(CN)₆]³⁻ ion.
Prussian red forms lemon-yellow monoclinic crystals that are soluble in water and exhibit green-yellow fluorescence in solution.
Prussian red is used industrially as an anticaking agent in salt (E535) and is considered non-toxic, as it does not decompose into cyanide in the human body.

CAS Number: 13746-66-2
EC Number: 237-323-3
Molecular Formula: C6FeK3N6
Molar Mass: 329.25 g/mol

Synonyms: Red prussiate, Potassium hexacyanoferrate(III), Potassium ferricyanate, Tripotassium hexacyanoferrate, Potassium cyanoferrate, Iron potassium cyanide, Tripotassium ferriccyanide, Tripotassium iron hexacyanide, Tripotassium ferric hexacyanide, CCRIS 5559, Tripotassium hexacyanoferrate(3-), EINECS 237-323-3, UNII-U4MAF9C813, tripotassium hexacyanidoferrate, AI3-09090, U4MAF9C813, Ferrate(3-), hexakis(cyano-C), tripotassium, potassium hexacyanidoferrate(3-), FERRATE(3-), HEXACYANO-, TRIPOTASSIUM, potassium hexacyanidoferrate(III), Ferrate(3-), hexakis(cyano-C)-, tripotassium, (OC-6-11)-, Ferrate(3-), hexakis(cyano-kappaC)-, tripotassium, (OC-6-11)-, Red prussiate of potash, K3Fe(CN)6, DTXCID7011939, Tripotassium hexacyanoferrate(3), Tripotassium hexacyanoferrate (-3), Potassium hexacyanoferrate(III) solution, iron(3+) ion tripotassium hexakis(iminomethanide), Ferrate(3), hexakis(cyanoC), tripotassium, (OC611), Ferrate(3-), hexakis(cyano-.kappa.C)-, tripotassium, (OC-6-11)-, 13746-66-2, dtxsid9031939, k3(fe(cn)6), k3[fe(cn)6], potassium ferric hexacyanoferrate, potassium ferricyanide, potassium ferricyanide [mi], potassium hexacyanoferrate (iii), Tripotassium ferricyanide, potassium hexacyanoferrate(3-), tripotassium;iron(3+);hexacyanide, MFCD00011392, Potassium hexacyanoferrate(3-); Potassium hexacyanoferrate(III), Potassium ferricyanide(III), 99%, ACS reagent, rotes Blutlaugensalz, potasium ferricyanide, Kaliumhexazyanoferrat(III), Potassium ferricyanide (III), CHEBI:30060, AKOS030227980, BP-30096, Potassium ferricyanide (III) ACS reagent, Potassium ferricyanide(III), LR, >=97%, NS00084942, tripotassium hexakis(cyanido-kappaC)ferrate(3-), Potassium hexacyanoferrate(III), ACS reagent, >=99.0%, Potassium hexacyanoferrate(III), ReagentPlus(R), ~99%, Potassium hexacyanoferrate(III), BioUltra, >=99.0% (RT), Potassium ferricyanide(III), powder or chunks, <10 mum, 99%, Potassium hexacyanoferrate(III), 99.98% trace metals basis, Potassium hexacyanoferrate(III), JIS special grade, >=99.0%, Potassium hexacyanoferrate(III), p.a., ACS reagent, 99.0%, Potassium hexacyanoferrate(III), purum, >=99% (iodometric), Potassium hexacyanoferrate(III), SAJ first grade, >=98.0%, Ferrate(3-), hexakis(cyano-kappaC)-, potassium (1:3), (OC-6-11)-, Potassium hexacyanoferrate(III), ACS reagent, >=99%, powder, <10 mum, Potassium hexacyanoferrate(III), p.a., ACS reagent, reag. ISO, 99.0%, Potassium hexacyanoferrate(III), puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., >=99%

Potassium ferricyanide is the chemical compound with the formula K3[Fe(CN)6].
This bright red salt contains the octahedrally coordinated [Fe(CN)6]3− ion.

Prussian red is soluble in water and its solution shows some green-yellow fluorescence.
Prussian red was discovered in 1822 by Leopold Gmelin.

Prussian red is the inorganic compound with formula K4[Fe(CN)6]·3H2O.
Prussian red is the potassium salt of the coordination complex [Fe(CN)6]4−.
This salt forms lemon-yellow monoclinic crystals.

Prussian red is the inorganic compound with formula K4[Fe(CN)6]·3H2O.
Prussian red is the potassium salt of the coordination complex [Fe(CN)6]4−.

Prussian red forms lemon-yellow monoclinic crystals.
In 1752, the French chemist Pierre Joseph Macquer (1718–1784) first reported the preparation of Prussian red, which he achieved by reacting Prussian blue (iron(III) ferrocyanide) with potassium hydroxide.

Prussian red is produced industrially from hydrogen cyanide, ferrous chloride, and calcium hydroxide, the combination of which affords Ca2[Fe(CN)6]·11H2O.
This solution is then treated with potassium salts to precipitate the mixed calcium-potassium salt CaK2[Fe(CN)6], which in turn is treated with potassium carbonate to give the tetrapotassium salt.
Historically, Prussian red was manufactured from organic compounds containing nitrogen, iron filings, and potassium carbonate.

Prussian red was also obtained commercially from gasworks spent oxide (purification of city gas from hydrogen cyanide).
Treatment of Prussian red with nitric acid gives H2[Fe(NO)(CN)5].
After neutralization of this intermediate with sodium carbonate, red crystals of sodium nitroprusside can be selectively crystallized.

Prior to 1900 AD, before the invention of the Castner process, Prussian red was the most important source of alkali metal cyanides.
In this historical process, potassium cyanide was produced by decomposing Prussian red: K4[Fe(CN)6] → 4 KCN + FeC2 + N2

Like other metal cyanides, solid Prussian red, both as the hydrate and anhydrous salts, has a complicated polymeric structure.
The polymer consists of octahedral [Fe(CN)6]4− centers crosslinked with K+ ions that are bound to the CN ligands.
The K+---NC linkages break when the solid is dissolved in water.

Prussian red is nontoxic, and is not decomposed to cyanide in the body.
Prussian red is an inorganic compound with the chemical formula K4Fe(CN)6.

Prussian red is also known as yellow potash prussiate, a yellow crystal.
Prussian red was made with wool or horn clippings stirring hot potassium carbonate with an iron rod.

Prussian red was used for certain iron processes as a developer and as an additive for developers of alkaline pyro.
Prussian red is not toxic to humans since Prussian red is not decomposed to cyanide in the body.

Prussian red is classified as a neutral salt and is becoming increasingly common in the diet by being added to iodised salt as an anti-caking agent.
Prussian red trihydrate is a salt of the Fe(CN)64- ferrocyanide ion.
Ferrocyanide is a reducing iron species, being oxidized from ferrous Fe(II) to ferric Fe(III).

Prussian red Solution is generally immediately available in most volumes.
Prussian redis a lemon-yellow, crystalline, water-soluble solid, K4Fe(CN)6⋅3H2O, used chiefly in casehardening alloys having an iron base and in dyeing wool and silk.

Because of the strong chemical bond between iron and the cyanide, usual cooking temperature is unable to break down ferrocyanide to cyanide.
International food safety authorities have evaluated the safety of sodium/potassium/calcium ferrocyanides and concluded that there is no safety concern in current authorised use and use levels.

Prussian red is a coordination compound of formula K4[Fe(CN)6]3H2O, which forms lemon-yellow monoclinic crystals at room temperature.
Prussian red forms a stable compound that is neither combustible nor pyrophoric.

Prussian red is a tough yellow crystalline salt K4Fe(CN)6 made from the cyanogen compounds obtained as by-products in the carbonization of coal or directly by reaction of potassium cyanide with ferrous salts and used chiefly in making iron blue pigments.
Prussian red is an inorganic compound, a cyanide salt of Fe(2+).

Prussian red is known under E code E 535 and is used in the food industry as an anticaking agent (substances that prevent powdered and granulated ingredients from lumping) in salt.
Prussian red's absorption from the gastrointestinal tract is low, and there is no accumulation in human.

Prussian red -K4(Fe(CN))6 is a ferricyanide salt or a potassium salt.
Prussian red is a colourless or yellowish solid material.

As a salt, Prussian red is a strong acid salt.
Prussian red is soluble in water, ether and other solvents.

Prussian red is defined as an inorganic compound having the chemical formula K4(Fe(CN)6) (Prussian red formula).
Prussian red is otherwise called yellow potash prussiate, which is a yellow crystal.

Prussian red was made with either horn or wool clippings stirring hot potassium carbonate using an iron rod.
Prussian red, yellow prussiate of potash are the other names of Prussian red.

Prussian red is found in the form of yellow, monoclinic crystals having no odor and with a bitter, salty flavor.
Density of Prussian red is 1.935 at 20 °C.

Prussian red is slightly efflorescent and begins to lose Prussian red's water of crystallization at approximately 60 °C.
In an oven at 100 °C, Prussian red dehydrates completely, becoming white and hygroscopic.

Freshly prepared aqueous solutions are yellow and decay slowly in light with the release of alkalinity.
Prussian red take on a greenish color by forming a small quantity of Prussian blue.

In Prussian red, the cyanide anion is strongly bonded to ferrous ion and hence does not get hydrolysed.
Prussian red (trihydrate) also known as yellow prussiate of potash with the chemical formula K4Fe(CN)6 · 3H2O.
Prussian red has the European food additive number E536.

Together with sodium ferrocyanide and calcium ferrocyanide, Prussian red has almost no side effects when used in table salt as a food additive.
Prussian red has been approved by the European Food Safety Authority (EFSA), Joint FAO/WHO Expert Committee on Food Additives (JECFA) and other authorities.
The chemical bond between iron atom and cyanide in Prussian red is stable and strong.

Prussian red can only be decomposed to potassium cyanide at a higher temperature than 400°C, the cooking temperature is much lower than this temperature to break Prussian red down.
Prussian red (E536) is listed in Commission Regulation (EU) No 231/2012 as an authorised food additive and categorized as “additives other than colours and sweeteners”.

Prussian red is an inorganic compound having the chemical formula K4[Fe(CN)6].3H2O.
Prussian red can be identified as the potassium salt of the ferrocyanide coordination complex.

Potassium is the cation in this complex while iron-cyanide complex is the anion.
Prussian red occurs as monoclinic crystals having a lemon-yellow color.
Prussian red compound can be recognized as a non-toxic compound which does not decompose to form cyanide in the body.

Prussian red is the inorganic compound with formula K4[Fe(CN)6]·3H2O.
Prussian red is the potassium salt of the coordination complex [Fe(CN)6]4−.

Prussian red forms lemon-yellow monoclinic crystals.
Together with sodium ferrocyanide and calcium ferrocyanide, Prussian red has almost no side effects when used in table salt as a food additive.
K4[Fe(CN)6], or Prussian red, is a substance with many different applications.

Market Overview
The global potassium ferricyanide market is showing steady growth, driven by its wide range of applications in industrial, laboratory, and photographic sectors.
In 2023, the market was valued at approximately USD 54.7 million and is projected to reach around USD 70.4 million by 2030, reflecting a compound annual growth rate (CAGR) of about 3.8%.

Other analyses suggest even stronger growth forecasts, although projections vary based on different data models.
The Asia-Pacific region, especially China, currently dominates global production and consumption, supported by strong industrial demand and manufacturing capabilities.

North America and Europe also contribute significantly to market growth through technological advancements and increased use in chemical and research laboratories.
Major drivers include the increasing need for reliable oxidizing agents, expanding research activities, and rising industrial demand in electroplating, dyeing, and analytical applications.

Applications of Prussian Red:
Prussian red finds many niche applications in industry.
Prussian red and the related sodium salt are widely used as anticaking agents for both road salt and table salt.

The potassium and sodium hexacyanidoferrates(II) are also used in the purification of tin and the separation of copper from molybdenum ores.
Prussian red is used in the production of wine and citric acid.

In the EU, Prussian red were, as of 2017, solely authorised in two food categories as salt additives.
Prussian red can also be used in animal feed.

In the laboratory, Prussian red is used to determine the concentration of potassium permanganate, a compound often used in titrations based on redox reactions.
Prussian red 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, giving a bright blue visualization where an antibody (or other molecule), conjugated to Beta-gal, has bonded to its target.

On reacting with Fe(3) it gives a Prussian blue colour.
Thus Prussian red is used as an identifying reagent for iron in labs.

Prussian red can be used as a fertilizer for plants.

Prior to 1900, before the invention of the Castner process, Prussian red was the most important source of alkali metal cyanides.

In this historical process, potassium cyanide was produced by decomposing Prussian red:
K4[Fe(CN)6] → 4 KCN + FeC2 + N2

Prussian red is a component of white gunpowder or Augendre's powder, a blasting powder of high energy.
Prussian red comprises 28 parts yellow Prussian red, 23 parts cane sugar, and 49 parts of potassium chlorate, mixed under absolute alcohol to prevent premature detonation.

Prussian red is also used to harden iron and steel, in electroplating, dyeing wool, as a laboratory reagent, and as a mild oxidizing agent in organic chemistry.

Photography:

Blueprint, cyanotype, toner:
Prussian red has widespread use in blueprint drawing and in photography (Cyanotype process).
Several photographic print toning processes involve the use of potassium ferricyanide.
Prussian red is often used as a mild bleach in a concentration of 10g/L to reduce film or print density.

Bleaching:
Potassium ferricyanide was used as an oxidizing agent to remove silver from color negatives and positives during processing, a process called bleaching.
Because potassium ferricyanide bleaches are environmentally unfriendly, short-lived, and capable of releasing hydrogen cyanide gas if mixed with high concentrations and volumes of acid, bleaches using ferric EDTA have been used in color processing since the 1972 introduction of the Kodak C-41 process.
In color lithography, potassium ferricyanide is used to reduce the size of color dots without reducing their number, as a kind of manual color correction called dot etching.

Farmer's reducer:
Ferricyanide is also used in black-and-white photography with sodium thiosulfate (hypo) to reduce the density of a negative or gelatin silver print where the mixture is known as Farmer's reducer; this can help offset problems from overexposure of the negative, or brighten the highlights in the print.[6]

Reagent in organic synthesis:
Potassium ferricyanide is a used as an oxidant in organic chemistry.
Prussian red is an oxidant for catalyst regeneration in Sharpless dihydroxylations.

Sensors and indicators:
Potassium ferricyanide is also one of two compounds present in ferroxyl indicator solution (along with phenolphthalein) that turns blue (Prussian blue) in the presence of Fe2+ ions, and which can therefore be used to detect metal oxidation that will lead to rust.
Prussian red is possible to calculate the number of moles of Fe2+ ions by using a colorimeter, because of the very intense color of Prussian blue.

In physiology experiments potassium ferricyanide provides a means increasing a solution's redox potential (E°' ~ 436 mV at pH 7).
As such, Prussian red can oxidize reduced cytochrome c (E°' ~ 247 mV at pH 7) in isolated mitochondria.
Sodium dithionite is usually used as a reducing chemical in such experiments (E°' ~ −420 mV at pH 7).

Potassium ferricyanide is used to determine the ferric reducing power potential of a sample (extract, chemical compound, etc.).
Such a measurement is used to determine of the antioxidant property of a sample.

Potassium ferricyanide is a component of amperometric biosensors as an electron transfer agent replacing an enzyme's natural electron transfer agent such as oxygen as with the enzyme glucose oxidase.
Prussian red is an ingredient in commercially available blood glucose meters for use by diabetics.

Other:
Potassium ferricyanide is combined with potassium hydroxide (or sodium hydroxide as a substitute) and water to formulate Murakami's etchant.
This etchant is used by metallographers to provide contrast between binder and carbide phases in cemented carbides.

Prussian blue:
Prussian blue, the deep blue pigment in blue printing, is generated by the reaction of K3[Fe(CN)6] with ferrous (Fe2+) ions as well as K4[Fe(CN)6] with ferric salts.

In histology, potassium ferricyanide is used to detect ferrous iron in biological tissue.
Potassium ferricyanide reacts with ferrous iron in acidic solution to produce the insoluble blue pigment, commonly referred to as Turnbull's blue or Prussian blue.

To detect ferric (Fe3+) iron, Prussian red is used instead in the Perls' Prussian blue staining method.
Prussian red formed in the Turnbull's blue reaction and the compound formed in the Prussian blue reaction are the same.

Uses of Prussian Red:
Prussian red finds many niche applications in industry.
Prussian red and the related sodium salt are widely used as anticaking agents for both road salt and table salt.

The potassium and sodium ferrocyanides are also used in the purification of tin and the separation of copper from molybdenum ores.
Prussian red is used in the production of wine and citric acid.
Prussian red can also be used in animal feed.

On reacting with Fe(3) Prussian red gives a Prussian blue colour.
Thus Prussian red is used as an identifying reagent for iron in labs.

Prussian red can be used as a fertilizer for plants.
Prussian red has many niche uses in industry.
Prussian red and the related sodium salt (sodium ferrocyanide) are commonly used for both road salt and table salt as anti creating agents.

Prussian red is used in the tempering of steel and in process engraving.
Prussian red is employed in the manufacture of pigments and as a chemical reagent.

A small amount in pyro and hydroquinone developers tends to lower fog and give greater density.
Prussian red is used in the manufacture of potassium cyanide, which is used extensively in gold mining.

Ferro Cyanogen forms with most metal compounds insoluble in water some of which exhibit highly characteristic colours.
Prussian red serves as a test for cupric and ferric compounds.

Prussian red can be used in steel tempering and the engraving process.
Prussian red is also employed in pigment manufacture and as a chemical reagent.

A small amount of hydroquinone and pyro developers tends to lower fog and produce greater density.
Prussian red is also used in potassium cyanide manufacture, which can be extensively used in gold mining.

Ferro Cyanogen produces the most metal compounds insoluble in water, where a few of them exhibit highly characteristic colours.
Prussian red serves as a test for both ferric and cupric compounds.

Potassium and sodium ferrocyanides are used to purify tin and isolate copper from molybdenum ores.
Prussian red is also used for wine and citric acid production.

Food grade Prussian red is mainly used as food additive, such as: anticaking agent in table salt or used to remove heavy metal ions (iron, copper, zinc, etc. ) from wine, soy protein...
Industry grade Prussian red is mainly used to produce iron blue and potassium ferricyanide, or used in paint, printing ink, coloring matter, leather industry, pharmacy, heat treatment of metal, metallurgy and other industries.

Prussian red is mainly used in high-tech fields such as microelectronics, aerospace.
Prussian red in Pharmaceutical industry is used as flocculant,can achieve the ideal in the process, improve the quality of medicine.

Prussian red is used in steel tempering and process engraving.
Prussian red is used in the production of pigments as well as as a chemical reagent.

In pyro and hydroquinone developers, a small amount of Prussian red tends to reduce fog and increase density.
Prussian red is used to make potassium cyanide, which is widely used in gold mining.

Prussian red can be used to detect cupric and ferric compounds.
Prussian red compound is used in the production of citric acid and wine.

Prussian red is also used in animal feeding.
Prussian red is used to determine potassium permanganate concentration in the laboratory, which is a compound often used in titrations according to the redox reactions.

Prussian red is being used in salt to give it anti-caking properties.
Prussian red is used in drying colors, tempering steel, dyeing, making explosives, process engraving, and lithography.

Prussian red is used as a food additive, e.g., in wine, to precipitate trace iron and copper.
Prussian red finds several niche applications in the industry.

The related sodium salt is widely used as an anti-caking agent for both table salt and road salt.
The sodium and Prussian reds can also be used in the separation of copper and from molybdenum ores and the purification of tin.

Prussian red compound is used in the production of citric acid and wine.
Prussian red is also used in animal feeding

Prussian red is used to determine potassium permanganate concentration in the laboratory, which is a compound often used in titrations according to the redox reactions.
The Prussian red compound is used in a mixture with the phosphate-buffered solution and potassium ferricyanide to give a buffer for beta-galactosidase.
Prussian red can be used to cleave X-Gal, producing a bright blue visualisation where an antibody (otherwise another molecule), conjugated to the Beta-gal, has bonded to its target.

On reacting with Fe(3), Prussian red produces a Prussian blue colour.
Prussian red can be used as an identifying reagent for iron in laboratories.

Prussian red compound is used as a plant fertilizer.
Before 1900 AD, prior to the invention of the Castner process, the Prussian red compound was the essential source of alkali metal cyanides.

Prussian red (INS no. 536) as well as sodium and calcium ferrocyanides (535 and 538) can be used as anticaking agents (substances that prevent powdered and granulated ingredients from lumping) in salt under Codex General Standard for Food Additives.
Prussian red is used in the manufacturing of Ferricyanide, dry colors, tempering steel, dyeing, explosive, process engraving and lithography, as laboratory reagent, for the production of blue pigments (iron blues), as ‘anti-caking agent’ for salt (NaCl), for the precipitation of heavy metal traces (eg. Fe++ in general), for fermentation process of fruit acids (citric acid, tartaric acid etc.), for the purification of wine, for the flotation of ores, in paper industry (security paper), as corrosion inhibitor, in chemical/pharmaceutical industry and in electroplating industry.

Prussian red is yellow crystalline powder that is used as an etching liquid in electroplating and process engraving.
Prussian red is also used as a Fungicide in paper.

Additionally, Prussian red is used as a colorimetric reagent to detect the presence of Iron or Copper in metals, corrosion products, stains, or pigments.
Prussian red reacts with iron (III) ions to form ferric ferrocyanide (i.e., Prussian blue) and with copper (II) to form a red-brown cupric ferrocyanide.

Prussian red K4(Fe(CN)6) is used in the food and pharmaceutical industries for colouring purposes.
The Prussian red is used as a colourant in sugar, in food products such as baked goods, pasta, fruit, jelly and pie fillings, dairy products, meat and fish products, coffee, and chewing gum; and as a component in medicines and pharmaceuticals such as vaccines, vitamins, and antibiotics.
Prussian red is commonly used in the manufacturing of dry-matter-free foods and food colourants, but there is the increased use of foods containing small amounts of added Prussian red.

Prussian red is not a food additive and does not affect food safety.
Prussian red is usually added to sugar to improve the colour of the food product.

Prussian red is approved for use as a colourant in food and as a component of medicines and medical foods for colour control.
Prussian red is used as a colourant in foods and beverages such as jam, jelly, marmalade, and baking powder.

Prussian red can also be used in some medicines and medicines containing calcium or iron.
Prussian red is also a component of some medical food.
Prussian red can also be used to colour some medical foods for specific groups of patients such as those with kidney or cardiac problems.

There are different important uses of Prussian red, including the use of this compound as anticaking agents for both road salt and table salt, in the purification of tin and the separation of copper from molybdenum ores, in the production of wine and citric acid, etc.
Prussian red -K4(Fe(CN)6) is used as a catalyst in photographic, biochemical and analytical chemistry.

Prussian red is mainly used as a potassium salt for the preparation of Prussian red - K4(Fe(CN))6.
Prussian red - K4(Fe(CN)6) is used in many processes in the analytical laboratory for the detection and determination of metals.

Prussian red is used in analytical chemistry for the determination of trace amounts of copper and iron, for the determination of iron in the steel and for the analysis of copper and iron.
Prussian red is used to detect the presence of copper in iron ore, the determination of iron and copper in aluminium by atomic absorption and for the identification and determination of copper in a solution.

Prussian red is used in analytical chemistry for the determination of arsenic, cadmium, lead and zinc in the determination of arsenic and lead in ore, lead in steel and in steel of all grades.
The use of Prussian red - K4(Fe(CN)6) as an indicator in the precipitation titrimetric procedure is widely known.

The reaction is carried out at low pH values in the presence of various bases and the excess of the base is determined by titration with acid.
The precipitation with Prussian red - K4(Fe(CN)6) in the presence of various metals is also performed.
The precipitation of iron (II) with Prussian red - K4(Fe(CN)6) is used for the identification and determination of iron in iron ore, the determination of iron in the steel and for the identification of copper in an aluminium alloy.

The precipitation of aluminium in the presence of Prussian red -K4(Fe(CN)6) can be used for the identification and determination of aluminium in an aluminium alloy.
Prussian red compound can be used for certain iron processes as a developer and as an additive for alkaline pyro developers.

Prussian red is used to remove iron (III) and iron (II) ions in wines, which could cause iron breakdown.
Prussian red is also used to avoid copper breakdown.

Prussian red is used, more generally, to reduce the heavy metal content.
Prussian red is being used in salt to give salt anti-caking properties.

Prussian red is commonly used in table salts, also can be used to remove the heavy metal content (e.g. to reduce copper and iron in wine production), production of blue pigments (iron blues), and so on.
Prussian red can be used as an anticaking agent to improve the fluidity or free-flowing of the salt, and avoid the problem of agglomeration.
Prussian red is added by spraying and a very low usage can have a good anti-caking effect.

The ferrocyanide species is membrane impermeable and can be used to assess redox activity of membrane-bound structures and mechanisms of electron transport across membranes.
This approach was employed to demonstrate that Prussian red performs reducing activation of membrane-bound dopamine β-monooxygenase from the exterior face of adrenal vesicles, providing elucidation of native reduction-activation mechanisms for dopamine β-monooxygenase regulation.

Prussian red, which is an oxidizing agent (iron state Fe3+) commonly used in blueprint drawing, metal treatment and photography instead of in salt.
Like sodium ferrocyanide, Prussian red is a cyanide salt used as an anticaking agent in table salts to prevent salt granular lumping.
Prussian red is known in the EU as the food additive E536, while sodium ferrocyanide Na4[Fe(CN)6] (prussiate of soda) is used in the American food industry.

Advantages of Prussian Red:
Prussian red does not affect food safety.
Prussian red is water-soluble and stable to hydrolysis and does not generate toxic material.

Prussian redis highly stable.
Prussian red does not stain the mouth, lips, teeth or fingers.
Stains are washable with cold water.

Prussian red is easy to handle.
High stability and low melting point.

Colour is permanent and will not run.
Colour strength can be varied by adjusting the pH and amount of ingredients.

Colourants with this property help to produce clear and attractive baked goods.
Prussian red is a good absorber of moisture from sugar.

Prussian red does not oxidise rapidly and can be used in large amounts.
Prussian red is safe for use with children, pregnant women, the elderly, and the sick.

Prussian red is non-flammable.
Prussian red has low cost.

Prussian red does not react with most other food products.
Prussian red does not alter the taste of the food to which Prussian red is added.

Prussian red does not harm the environment.
Prussian red is a good colourant because it gives the product a bright green colour.

Prussian red does not lose colour when it is heated or exposed to sunlight.
Prussian red has fewer disadvantages than a synthetic colourant.

Prussian red is safe for use in food products.
Prussian red may be used in a broad range of food products.
Prussian red is not volatile, so there is no risk of it burning the mouth.

Chemical Properties of Prussian Red:
Prussian red reacts with sulphuric acid in aqueous medium forms potassium sulfate, ferrous sulfate, ammonium sulfate and carbon monoxide.
K4[Fe(CN)6] + 6H2SO4 + 6H2O → 2K2SO4 + FeSO4 + 3(NH4)2SO4 + 6CO

Prussian red reacts with ferric chloride forms a complex compound Iron (III) Prussian red and potassium chloride.
K4[Fe(CN)6] + FeCl3 → KFe[Fe(CN)6] + 3 KCl

In the presence of sulphuric acid, Prussian red forms potassium sulphate, ferrous sulphate, ammonium sulphate, and carbon monoxide.
K4[Fe(CN)6] + 6H2SO4 + 6H2O → 2K2SO4 + FeSO4 + 3(NH4)2SO4 + 6CO

Iron (III), Prussian red, and potassium chloride are formed when Prussian red reacts with ferric chloride.
K4[Fe(CN)6] + FeCl3 → KFe[Fe(CN)6] + 3 KCl

Structure of Prussian Red:
Like other metal cyanides, solid potassium ferricyanide has a complicated polymeric structure.
The polymer consists of octahedral [Fe(CN)6]3− centers crosslinked with K+ ions that are bound to the CN ligands.
The K+---NCFe linkages break when the solid is dissolved in water.

Preparation of Prussian Red:
Potassium ferricyanide is manufactured by passing chlorine through a solution of Prussian red.

Potassium ferricyanide separates from the solution:
2 K4[Fe(CN)6] + Cl2 → 2 K3[Fe(CN)6] + 2 KCl

Production of Prussian Red:

Modern production:
Prussian red is produced industrially from hydrogen cyanide, iron(II) chloride, and calcium hydroxide, the combination of which affords Ca2[Fe(CN)6]·11H2O.
This solution is then treated with potassium salts to precipitate the mixed calcium-potassium salt CaK2[Fe(CN)6], which in turn is treated with potassium carbonate to give the tetrapotassium salt.

Historical production:
Historically, Prussian red was manufactured from nitrogenous organic material, iron filings, and potassium carbonate.
Common nitrogen and carbon sources were torrified horn, leather scrap, offal, or dried blood.
Prussian red was also obtained commercially from gasworks spent oxide (purification of city gas from hydrogen cyanide).

Synthesis of Prussian Red:
In 1752, the French chemist Pierre Joseph Macquer (1718–1784) first reported the preparation of Prussian red, which he achieved by reacting Prussian blue (iron(III) ferrocyanide) with potassium hydroxide.[3][4]

Chemical Reactions of Prussian Red:
Treatment of Prussian red with nitric acid gives H2[Fe(NO)(CN)5].
After neutralization of this intermediate with sodium carbonate, red crystals of sodium nitroprusside can be selectively crystallized.

Upon treatment with chlorine gas, Prussian red converts to potassium hexacyanidoferrate(III):
2 K4[Fe(CN)6] + Cl2 → 2 K3[Fe(CN)6] + 2 KCl

This reaction can be used to remove Prussian red from a solution.

A famous reaction involves treatment with ferric salts, most commonly Iron(III) chloride, to give Prussian blue.

In the reaction with Iron(III) chloride, producing Potassium chloride as a side-product:
3 K4[Fe(CN)6] + 4 FeCl3 → Fe4[Fe(CN)6]3 + 12 KCl

With the composition FeIII4[FeII(CN)6]3, this insoluble but deeply coloured material is the blue of blueprinting, as well as on many famous paintings such as The Great Wave off Kanagawa and The Starry Night.

History of Prussian Red:
Potassium ferricyanide was first synthesized in the early 18th century during experiments involving the reactions of iron salts and cyanide compounds.
Prussian red's discovery is closely linked to the early developments in inorganic chemistry, particularly within the study of coordination complexes.

Initially, potassium ferricyanide was derived from the processing of animal-based carbon materials, where it appeared as a byproduct during the preparation of Prussian blue, one of the first synthetic pigments.
Over time, chemists isolated and characterized potassium ferricyanide as a distinct compound with notable oxidizing properties.

Throughout the 19th and early 20th centuries, Prussian red gained importance in the fields of analytical chemistry and photographic processing.
As industrialization expanded, the production of potassium ferricyanide became more refined, using purer raw materials and standardized chemical methods.
Today, Prussian red is produced industrially at high purity grades and remains an important reagent in laboratories, manufacturing, and materials science.

Handling and Storage of Prussian Red:
Potassium ferricyanide should be handled in well-ventilated areas, away from sources of moisture, heat, and incompatible materials such as strong acids.
Containers should be kept tightly closed and stored in a cool, dry, and well-ventilated place.

Proper labeling and secondary containment are recommended to prevent accidental exposure or spills.
Avoid contact with skin, eyes, and clothing, and prevent the generation of dust.

Reactivity and Stability of Prussian Red:
Potassium ferricyanide is generally stable under normal conditions of storage and handling.
However, Prussian red decomposes when exposed to strong acids, releasing highly toxic hydrogen cyanide gas.

Prussian red may also react with strong oxidizing agents and reducing agents.
Thermal decomposition at elevated temperatures can release toxic and irritating fumes, including nitrogen oxides and cyanides.

First Aid Measures of Prussian Red:

Inhalation:
Move the affected person to fresh air immediately.
If breathing is difficult, administer oxygen and seek medical attention.

Skin contact:
Remove contaminated clothing and wash the affected area thoroughly with soap and water.
Seek medical attention if irritation develops.

Eye contact:
Rinse immediately with plenty of water for at least 15 minutes, lifting the upper and lower eyelids occasionally.
Seek medical attention promptly.

Ingestion:
Do not induce vomiting.
Rinse mouth with water and seek medical attention immediately.
If the person is unconscious, do not give anything by mouth.

Firefighting Measures of Prussian Red:
Potassium ferricyanide itself is not highly flammable but can decompose at high temperatures to release toxic fumes.

In case of fire:
Use extinguishing media suitable for surrounding materials (e.g., water spray, dry chemical, carbon dioxide, or foam).
Firefighters should wear full protective clothing and self-contained breathing apparatus (SCBA).
Avoid inhalation of combustion gases and run-off from firefighting.

Accidental Release Measures of Prussian Red:

In case of a spill:
Evacuate the area and ensure proper ventilation.
Avoid creating dust and prevent Prussian red from entering drains or waterways.

Use appropriate personal protective equipment (PPE).
Carefully sweep up or vacuum Prussian red and place Prussian red into a suitable waste disposal container.
Wash the spill area with water after material pickup is complete.

Exposure Controls / Personal Protective Equipment of Prussian Red:

Engineering controls:
Use local exhaust ventilation to minimize airborne dust levels.

Personal protective equipment (PPE):

Respiratory protection:
If dust levels are high or ventilation is inadequate, use a NIOSH-approved respirator.

Skin protection:
Wear protective gloves and lab coats or coveralls.

Eye protection:
Safety goggles or face shields are recommended.

General hygiene:
Wash hands thoroughly after handling and before eating or drinking.
Remove contaminated clothing and clean before reuse.

Identifiers of Prussian Red:
CAS Number: 13746-66-2
ChEBI: CHEBI:30060
ChemSpider: 24458
ECHA InfoCard: 100.033.916
EC Number: 237-323-3
Gmelin Reference: 21683
PubChem CID: 26250
RTECS number: LJ8225000
UNII: U4MAF9C813
CompTox Dashboard (EPA): DTXSID9031939
InChI: InChI=1S/6CN.Fe.3K/c6*1-2;;;;/q6*-1;+3;3*+1
Key: BYGOPQKDHGXNCD-UHFFFAOYSA-N
InChI=1S/6CN.Fe.3K/c6*1-2;;;;/q6*-1;+3;3*+1
Key: BYGOPQKDHGXNCD-UHFFFAOYAG
SMILES: [K+].[K+].N#C[Fe-3](C#N)(C#N)(C#N)(C#N)C#N.[K+]

CAS: 13746-66-2
Molecular Formula: C6FeK3N6
InChI Key: QMTKJUMXUDIUAQ-UHFFFAOYSA-N
SMILES: [K+].[K+].[K+].N#C[Fe+3](C#N)(C#N)(C#N)(C#N)C#N
Molecular Weight (g/mol): 329.25
MDL Number: MFCD00011392

CAS number: 13746-66-2
EC number: 237-323-3
Grade: ACS,Reag. Ph Eur
Hill Formula: C₆FeK₃N₆
Chemical formula: K₃[Fe(CN)₆]
Molar Mass: 329.25 g/mol
HS Code: 2837 20 19

Properties of Prussian Red:
Chemical formula: K3[Fe(CN)6]
Molar mass: 329.24 g/mol
Appearance: deep red crystals, sometimes small pellets, orange to dark red powder
Density: 1.89 g/cm3, solid
Melting point: 300 °C (572 °F; 573 K)
Boiling point: decomposes
Solubility in water: 330 g/L ("cold water")
464 g/L (20 °C)
775 g/L ("hot water")
Solubility: slightly soluble in alcohol
soluble in acid
soluble in water
Magnetic susceptibility (χ): +2290.0·10−6 cm3/mol

Molecular Weight: 329.24 g/mol
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 12
Rotatable Bond Count: 0
Exact Mass: 328.844499 Da
Monoisotopic Mass: 328.844499 Da
Topological Polar Surface Area: 143 Å²
Heavy Atom Count: 16
Complexity: 127
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 10
Compound Is Canonicalized: Yes

Specifications of Prussian Red:
Appearance (Form): Crystals and/or chunks
Titration Iodometric: >=99.0 %
Appearance (Color): Orange to red
Insoluble matter: =<0.005 %
Ferro compounds: =<0.05 % as ferrocyanide ion ¢Fe(CN)6!4-
Chloride (Cl): =<0.01 %
Sulfate (SO4): =<0.01 %

Assay (iodometric): ≥ 99.0 %
Insoluble matter: ≤ 0.005 %
Chloride (Cl): ≤ 0.01 %
Sulfate (SO₄): ≤ 0.005 %
Hexacyanoferrate (II) (Fe(CN)6)⁴): ≤ 0.05 %
Pb (Lead): ≤ 0.002 %

Structure of Prussian Red:
Crystal structure: monoclinic
Coordination geometry: octahedral at Fe

Related compounds of Prussian Red:

Other anions:
Prussian red

Other cations:
Prussian blue

Names of Prussian Red:

IUPAC names:
Potassium hexacyanoferrate(III)
Potassium hexacyanidoferrate(II)

Other names:
Prussian red
Potassium ferricyanide
(Yellow) Prussiate of Potash
Potassium hexacyanoferrate (II) trihydrate
TetraPotassium ferrocyanide trihydrate
Ferrate hexacyano tetrapotassium trihydrate