WHAT IS POTASSIUM FERROCYANIDE
Potassium ferrocyanide occurs as odourless, light yellow crystals which are soluble in water but insoluble in alcohols. Also known as yellow prussiate of potash or potassium hexacyanoferrate(II), Potassium ferrocyanide is manufactured from hydrogen ferrocyanide and potassium hydroxide. It is not considered to be toxic but is dangerous when heated or mixed with other chemicals. It is commonly used as a laboratory reagent and in the production of dyes, pigments and paints.
- Synonyms: potassium hexacyanoferrate(II); Potassium hexacyanidoferrate(II); yellow prussiate of potash, tetrapotassium ferrocyanide; potassium prussiate trihydrate; tetrapotassium hexacyanidoferrate (4-), trihydrate;
- Formula: C6N6FeK4.3(H2O) or K4[Fe(CN)6].3(H2O)
- Appearance: yellow crystals
- Mol weight: 422.41
- Purity: 98+%
- CAS no: 14459–95–1
- EINECS no: 237–722–2
- Density: 1.85
- Melting Point: 69–71C
- Boiling Point: 400C decomposes
- Solubility: soluble in water 211g/L @20C
- pH: 8–10
It is Stable under normal temperatures and pressures; decomposes on strong heating to evolve highly toxic fumes of hydrogen cyanide gas. It is not compatible with many reagents including strong oxidising agents and acids.
Uses for Potassium ferrocyanide
Potassium ferrocyanide finds many niche applications in industry. It and the related sodium salt are widely used as anti-caking agents for both road salt and table salt. Potassium ferrocyanide is also used in the purification of tin and the separation of copper from molybdenum ores. It is used to harden iron alloys. It is used in the dying of of wool and silk. Other uses include in metal extraction and to make adhesives, computer electronics, fire retardants, cosmetics, dyes, nylon, paints, inks and plexiglass.
Food grade Potassium ferrocyanide is used in the production of wine and citric acid. It is used to remove copper from wine where copper has been used as a fungicide.
Potassium ferrocyanide can be used as a fertilizer for plants.
It is used in the production of potassium ferricyanide.
Potassium ferrocyanide in the laboratory
In the laboratory potassium ferrocyanide is used to determine the concentration of potassium permanganate and is a qualitative test for copper and molybdenum. Potassium ferrocyanide is used to prepare the red crystals of sodium nitroprusside by treating with nitric acid and then neutralising the solution with sodium carbonate.
When heated it decomposes to produce potassium cyanide (KCN), iron, nitrogen and carbon.
When added to hot dilute sulphuric acid hydrogen cyanide is formed but when heating with concentrated sulphuric acid carbon monoxide is evolved.
Potassium ferrocyanide used to prepare Prussian Blue
Potassium ferrocyanide is used to prepare Prussian Blue, the deep blue pigment in blue printing. It is produced by the reaction of K4[Fe(CN)6] with ferric (Fe3+) ions.
Health & safety
R32 Contact with acids liberates very toxic gas. R52/53 Harmful to aquatic organisms, may cause long-term adverse effects in the aquatic environment.
S2– S22 Do not breathe dust. S24/25 Avoid contact with skin and eyes. S47 Keep at temperature not exceeding 50 C. S61 Avoid release to the environment. Refer to special instructions/ Safety data sheets
For full fetails see MSDS for Potassium ferrocyanide