Sodium ferrocyanide
Encyclopedia
Sodium ferrocyanide is the sodium salt of the coordination compound
of formula [Fe(CN)6]4-. It is a yellow crystal
line solid that is soluble in water and insoluble in alcohol
. Despite the presence of the cyanide ligands, sodium ferrocyanide is not especially toxic (acceptable daily intake 0–0.025 mg/(kg body weight)) because the cyanides are tightly bound to the metal. In its hydrous
form, Na4Fe(CN)6·10H2O (sodium ferrocyanide decahydrate), it is sometimes known as yellow prussiate of soda. The yellow color is the color of ferrocyanide
anion.
as an anticaking agent
. When combined with iron, it converts to a deep blue pigment called Prussian blue
. In photography, it is used for bleaching, toning, and fixing. It is used as a stabilizer for the coating on welding
rods. In the petroleum
industry, it is used for removal of mercaptans.
, the combination of which affords Ca2[Fe(CN)6].11H2O. A solution of this salt is then treated with sodium salts to precipitate the mixed calcium-sodium salt CaNa2[Fe(CN)6], which in turn is treated with sodium carbonate to give the tetrasodium salt.
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
of formula [Fe(CN)6]4-. It is a yellow crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
line solid that is soluble in water and insoluble in alcohol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
. Despite the presence of the cyanide ligands, sodium ferrocyanide is not especially toxic (acceptable daily intake 0–0.025 mg/(kg body weight)) because the cyanides are tightly bound to the metal. In its hydrous
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
form, Na4Fe(CN)6·10H2O (sodium ferrocyanide decahydrate), it is sometimes known as yellow prussiate of soda. The yellow color is the color of ferrocyanide
Ferrocyanide
Ferrocyanide is the name of the anion Fe64−. In aqueous solutions, this coordination complex is relatively unreactive. It is usually available as the salt potassium ferrocyanide, which has the formula K4Fe6....
anion.
Uses
Sodium ferrocyanide is a chemical additive known as E 535. It is added to road and food grade saltSalt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
as an anticaking agent
Anticaking agent
An anticaking agent is an additive placed in powdered or granulated materials, such as table salt, to prevent the formation of lumps, easing packaging, transport, and consumption....
. When combined with iron, it converts to a deep blue pigment called Prussian blue
Prussian blue
Prussian blue is a dark blue pigment with the idealized formula Fe718. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents....
. In photography, it is used for bleaching, toning, and fixing. It is used as a stabilizer for the coating on welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
rods. In the petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
industry, it is used for removal of mercaptans.
Production
Sodium ferrocyanide is produced industrially from hydrogen cyanide, ferrous chloride, and calcium hydroxideCalcium hydroxide
Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or...
, the combination of which affords Ca2[Fe(CN)6].11H2O. A solution of this salt is then treated with sodium salts to precipitate the mixed calcium-sodium salt CaNa2[Fe(CN)6], which in turn is treated with sodium carbonate to give the tetrasodium salt.