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Potassium ferrocyanide trihydrate [14459-95-1]
| Identification | ||
| Name | Potassium ferrocyanide trihydrate | |
| Synonyms | Potassium hexacyanoferrate(II) trihyrate | |
| Molecular Formula | K4.[Fe(CN)6].3(H2O) | |
| Molecular Weight | 422.36 | |
| CAS Registry Number | 14459-95-1 | |
| Properties | ||
| Density | 1.85 | |
| Melting point | 70 ºC | |
| Water solubility | 270 g/L (12 ºC) | |
Applications
Potassium ferrocyanide 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 ferrocyanides are also used in the purification of tin and the separation of copper from molybdenum ores. Potassium ferrocyanide is used in the production of wine and citric acid.[4]
In the EU, ferrocyanides (E 535-538) were, as of 2018, solely authorised in two food categories as salt substitutes. Kidneys are the organ for ferrocyanide toxicity.[7]
It can also be used in animal feed.[8]
In the laboratory, potassium ferrocyanide is used to determine the concentration of potassium permanganate, a compound often used in titrations based on redox reactions. Potassium ferrocyanide is used in a mixture with potassium ferricyanide and phosphate buffered solution to provide a buffer for beta-galactosidase, which is used to cleave X-Gal, giving a bright blue visualization where an antibody (or other molecule), conjugated to Beta-gal, has bonded to its target. On reacting with Fe(3) it gives a Prussian blue colour. Thus it is used as an identifying reagent for iron in labs.
Potassium ferrocyanide can be used as a fertilizer for plants.[citation needed]
Prior to 1900 AD, before the invention of the Castner process, potassium ferrocyanide was the most important source of alkali metal cyanides.[4] In this historical process, potassium cyanide was produced by decomposing potassium ferrocyanide:[5]
K4[Fe(CN)6] → 4 KCN + FeC2 + N2
Structure
Like other metal cyanides, solid potassium ferrocyanide, both as the hydrate and anhydrous salts, has a complicated polymeric structure. The polymer consists of octahedral [Fe(CN)6]4− centers crosslinked with K+ ions that are bound to the CN ligands.[9] The K+---NC linkages break when the solid is dissolved in water.
Toxicity
Potassium ferrocyanide is nontoxic, and is not decomposed to cyanide in the body. The toxicity in rats is low, with lethal dose (LD50) at 6400 mg/kg.[2]
