Potassium Ferrocyanide

Potassium ferrocyanide is used in wine to eliminate excess iron and copper. Recognised by the OIV, potassium ferrocyanide is permitted for use in grape wine in over 40 countries worldwide. 

Potassium hexacyanoferrate (II) is found in the form of yellow, monoclinic crystals having no odor and with a bitter, salty flavor. Density is 1.935 at 20 °C. This salt is slightly efflorescent and begins to lose its water of crystallization at approximately 60 °C. In an oven at 100 °C, it dehydrates completely, becoming white and hygroscopic. Freshly prepared aqueous solutions are yellow and decay slowly in light with the release of alkalinity. They take on a greenish color by forming a small quantity of Prussian blue. Potassium hexacyanoferrate (II) is used to remove iron (III) and iron (II) ions in wines, which could cause iron breakdown. It is also used to avoid copper breakdown. It is used, more generally, to reduce the heavy metal content. It use must be strictly controlled by mandatory monitoring.Potassium hexacyanoferrate (II) is found in the form of yellow, monoclinic crystals having no odor and with a bitter, salty flavor. Density is 1.935 at 20 °C. This salt is slightly efflorescent and begins to lose its water of crystallization at approximately 60 °C. In an oven at 100 °C, it dehydrates completely, becoming white and hygroscopic. Freshly prepared aqueous solutions are yellow and decay slowly in light with the release of alkalinity. They take on a greenish color by forming a small quantity of Prussian blue. Potassium hexacyanoferrate (II) is used to remove iron (III) and iron (II) ions in wines, which could cause iron breakdown. It is also used to avoid copper breakdown. It is used, more generally, to reduce the heavy metal content. It use must be strictly controlled by mandatory monitoring. 

The aqueous solution at 1 pp 100 (m/v) yields hexacyanoferrate (II) ion and potassium reactions, particularly with the iron (III) cation, resulting in a dark blue iron (III) hexacyanoferrate (II) (Prussian blue) precipitate which is insoluble in dilute mineral acids. With the copper cation, it forms a purple copper (II) hexacyanoferrate (II) precipitate that is insoluble in dilute mineral acids. For further substance information, please see the International Oenological Codex.