Cobalt(II) fluoride
Encyclopedia
Cobalt fluoride is a chemical compound
with the formula (CoF2). It is a pink crystalline solid compound. The formula is given for both the red tetragonal crystal, (CoF2), and the tetrahydrate red orthogonal crystal, (CoF2 •4H2O). CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it has public health uses.
CoF2 is sparingly soluble in water. The compound can be dissolved in warm mineral acid, and will decompose in boiling water. Yet the hydrate is water soluble, especially the di-hydrate CoF2 •2H2 O and tri-hydrate CoF2 •3H2O forms of the compound. The hydrate will also decompose with heat.
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It is produced in the reaction of cobalt (III) fluoride with water.
The tetrahydrate
cobalt(II) fluoride is formed by dissolving cobalt(II) in hydrofluoric acid. The anhydrous fluoride can be extracted from this by dehydration. Other synthesis can occur at higher temperatures. It has been shown that at 500°C fluorine will combine with cobalt producing a mixture of CoF2 and CoF3.
for the cobalt. A small amount of salt can be dissolved in cold water and analyzed for fluoride ion by a fluoride ion-selective electrode or ion chromatography
. Analysis of the elemental composition reveals Co 60.80%, F 39.20%.
. Cobalt(II) complexes are usually octahedral or tetrahedral. As a 19-electron species it is a good reducing agent, fairly oxidizable into an 18-electron compound. Cobalt(II) fluoride can be reduced by hydrogen at a 300° C.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula (CoF2). It is a pink crystalline solid compound. The formula is given for both the red tetragonal crystal, (CoF2), and the tetrahydrate red orthogonal crystal, (CoF2 •4H2O). CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it has public health uses.
CoF2 is sparingly soluble in water. The compound can be dissolved in warm mineral acid, and will decompose in boiling water. Yet the hydrate is water soluble, especially the di-hydrate CoF2 •2H2 O and tri-hydrate CoF2 •3H2O forms of the compound. The hydrate will also decompose with heat.
Preparation
Cobalt(II) fluoride can be prepared from anhydrous cobalt(II) chloride or cobalt(II) oxide in a stream of hydrogen fluorideHydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
:
- CoCl2 + 2HF → CoF2 + 2HCl
- CoO + 2HF → CoF2 + H2 O
It is produced in the reaction of cobalt (III) fluoride with water.
The tetrahydrate
Tetrahydrate
A tetrahydrate is a molecule surrounded by four molecules of water, forming a hydrate. The notation for a tetrahydrate is anhydrous molecule's formula·4H2O, where the 4 represents tetrahydrate, and the H2O represents the tetrahydrate. And the molecule's name changes to anhydrous molecule's name...
cobalt(II) fluoride is formed by dissolving cobalt(II) in hydrofluoric acid. The anhydrous fluoride can be extracted from this by dehydration. Other synthesis can occur at higher temperatures. It has been shown that at 500°C fluorine will combine with cobalt producing a mixture of CoF2 and CoF3.
Uses
Cobalt(II) fluoride can be used as a catalyst to alloy metals. It is also used for optical deposition, of which it tremendously improves optical quality. Cobalt(II) fluoride is available in most volumes in an ultra high purity composition. High purity compositions improve optical qualities and its usefulness as a standard. The compound may be used in dental care, since fluoride is also used in dental care.Analysis
To analysis this compound, Cobalt (II) fluoride can be dissolved in nitric acid. The solution is then diluted with water until appropriate concentration for AA or ICP spectrophotometrySpectrophotometry
In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength...
for the cobalt. A small amount of salt can be dissolved in cold water and analyzed for fluoride ion by a fluoride ion-selective electrode or ion chromatography
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
. Analysis of the elemental composition reveals Co 60.80%, F 39.20%.
Chemical Properties
CoF2 is a weak Lewis acidLewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
. Cobalt(II) complexes are usually octahedral or tetrahedral. As a 19-electron species it is a good reducing agent, fairly oxidizable into an 18-electron compound. Cobalt(II) fluoride can be reduced by hydrogen at a 300° C.