What Is Potassium Ferrocyanide?
Potassium ferrocyanide, an inorganic compound with the chemical formula K4[Fe(CN)6], is also known as potassium hexacyanoferrate(II) and yellow prussiate of potash. This complex salt, often encountered as a trihydrate, has a historical synthesis involving the heating of animal blood and bone with iron and potassium carbonate.
It is recognized as a hazardous substance under industrial safety regulations, requiring specific handling and labeling precautions.
Uses of Potassium Ferrocyanide
Its applications include use as a developer in blueprinting, a reagent for iron ion detection, and a stabilizer for iron, copper, and silver. In microscopy, it serves as a staining agent, enhancing contrast due to its interaction with heavy metals. Additionally, it is utilized in the food industry as an anti-caking agent for salt, approved for this purpose despite initial safety concerns.
1. Detection of Iron (II) Ions
In aqueous solutions, potassium ferrocyanide reacts with iron(II) ions to form a blue-white precipitate, while with iron(III) ions, it produces dark blue precipitates, known as Prussian blue.
2. Food Additives
Now approved as a food additive, potassium ferrocyanide prevents clumping in salt. Its use is restricted to this application, reflecting regulatory oversight concerning its addition to foods.
Properties of Potassium Ferrocyanide
The anhydrous form has a molecular weight of 368.4 and exists as a hygroscopic, colorless powder. The trihydrate variant, appearing as yellow crystals or powder, has a molecular weight of 422.39 and a melting point of 70°C. Soluble in water and virtually insoluble in ethanol, its solutions are pale yellow.
Types of Potassium Ferrocyanide
Available primarily for research, it is sold as a trihydrate or a 1% solution, in quantities suitable for laboratory use.
Other Information on Potassium Ferrocyanide
1. Synthesis of Potassium Ferrocyanide
This compound can be synthesized from sodium cyanide, iron(II) sulfate, and potassium chloride, showcasing its versatile preparation methods.
2. Chemical Reaction of Potassium Ferrocyanide
The ferrocyanide ion [Fe(CN)6]4− is stable and non-toxic in aqueous solutions, contrasting with the hazardous nature of free cyanide ions. However, its decomposition can occur under certain conditions, such as in the presence of hot dilute sulfuric acid, releasing hydrogen cyanide.