Potassium ferricyanide

Potassium ferricyanide

Names
IUPAC name Potassium hexacyanoferrate(III)
Other names Red prussiate of Potash, Prussian red, Potassium ferricyanide
Identifiers
CAS Number	13746-66-2 Y
3D model (Jmol)	Interactive image
ChemSpider	24458 N
ECHA InfoCard	100.033.916
PubChem	26250
RTECS number	LJ8225000
InChI InChI=1S/6CN.Fe.3K/c6*1-2;;;;/q6*-1;+3;3*+1 N Key: BYGOPQKDHGXNCD-UHFFFAOYSA-N N InChI=1S/6CN.Fe.3K/c6*1-2;;;;/q6*-1;+3;3*+1 Key: BYGOPQKDHGXNCD-UHFFFAOYAG
SMILES [C-]#N.[C-]#N.[C-]#N.[C-]#N.[C-]#N.[C-]#N.[K+].[K+].[K+].[Fe+3]
Properties
Chemical formula	K3[Fe(CN)6]
Molar mass	329.24 g/mol
Appearance	deep red crystals, sometimes small pellets, orange to dark red powder
Density	1.89 g/cm3, solid
Melting point	300 °C (572 °F; 573 K)
Boiling point	decomposes
Solubility in water	330 g/L ("cold water") 464 g/L (20 °C) 775 g/L ("hot water")
Solubility	slightly soluble in alcohol soluble in acid soluble in water
Magnetic susceptibility (χ)	+2290.0·10−6 cm3/mol
Structure
Crystal structure	monoclinic
Coordination geometry	octahedral at Fe
Hazards
Safety data sheet	MSDS
R-phrases	R20, R21, R22, R32
S-phrases	S26, S36
Flash point	Non-flammable
Related compounds
Other anions	Potassium ferrocyanide
Other cations	Prussian blue
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Potassium ferricyanide is the chemical compound with the formula K₃[Fe(CN)₆]. This bright red salt contains the octahedrally coordinated [Fe(CN)₆]³⁻ ion. It is soluble in water and its solution shows some green-yellow fluorescence.

Potassium ferricyanide is manufactured by passing chlorine through a solution of potassium ferrocyanide. Potassium ferricyanide separates from the solution:

Like other metal cyanides, solid potassium ferricyanide has a complicated polymeric structure. The polymer consists of octahedral [Fe(CN)₆]³⁻ centers crosslinked with K⁺ ions that are bound to the CN ligands. The K⁺---NCFe linkages break when the solid is dissolved in water.

In the 19th century, it was used for reading palimpsests and old manuscripts.

The compound has widespread use in blueprint drawing and in photography (Cyanotype process). Several photographic print toning processes involve the use of potassium ferricyanide. Potassium ferricyanide is used as an oxidizing agent to remove silver from negatives and positives, a process called dot etching. In color photography, potassium ferricyanide is used to reduce the size of color dots without reducing their number, as a kind of manual color correction. It is also used in black-and-white photography with sodium thiosulfate (hypo) to reduce the density of a negative or gelatin silver print where the mixture is known as Farmer's reducer; this can help offset problems from overexposure of the negative, or brighten the highlights in the print.