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Sodium ferrocyanide is produced industrially from hydrogen cyanide, ferrous chloride, and calcium hydroxide, the combination of which affords Ca 2 [Fe(CN) 6]·11H 2 O.A solution of this salt is then treated with sodium salts to precipitate the mixed calcium-sodium salt CaNa 2 [Fe(CN) 6] 2, which in turn is treated with sodium carbonate to give the tetrasodium salt.
Ferrocyanide is the name of the anion [Fe 6] 4−. Salts of this coordination complex give yellow solutions. It is usually available as the salt potassium ferrocyanide, which has the formula K 4 Fe(CN) 6. [Fe(CN) 6] 4− is a diamagnetic species, featuring low-spin iron(II) center in an octahedral ligand environment.
Prussian white, also known as Berlin white or Everett's salt, is the sodium end-member of the totally reduced form of the Prussian blue in which all iron is present as Fe(II). It is a sodium hexacyanoferrate of Fe(II) of formula Na 2 Fe[Fe(CN) 6]. [29] Its molecular weight value is 314 g/mol. [29]
The iron is low spin and easily reduced to the related ferrocyanide ion [Fe(CN) 6] 4−, which is a ferrous (Fe 2+) derivative. This redox couple is reversible and entails no making or breaking of Fe–C bonds: [Fe(CN) 6] 3− + e − ⇌ [Fe(CN) 6] 4−. This redox couple is a standard in electrochemistry.
500 sodium bicarbonate; 535 sodium ferrocyanide; 536 potassium ferrocyanide; 538 calcium ferrocyanide; 542 calcium phosphate; 550 sodium silicate; 551 silicon dioxide; 552 calcium silicate; 553a magnesium trisilicate; 553b talcum powder; 554 sodium aluminosilicate; 555 potassium aluminium silicate; 556 calcium aluminosilicate; 558 bentonite ...
Potassium hexacyanidoferrate(II) finds many niche applications in industry. It 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.
The nitrogen terminus is a good ligand for other metals. The latter tendency is illustrated by the condensation of ferrocyanide salts with other metal ions to give polymers, such as Prussian blue. Such polymers feature Fe-CN-M linkages.
Ferroxyl indicator, or rust indicator, is a solution containing potassium hexacyanoferrate(III), phenolphthalein and sodium chloride. It turns blue in the presence of Fe 2+ ions, and pink in the presence of hydroxide (OH −) ions. It can be used to detect metal oxidation, and is often used to detect rusting in various situations.