Cobalt(II) fluoride is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula (CoF₂). It is a pink crystalline solid compound which is

antiferromagnetic In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. ...

at low temperatures (T_N=37.7 K) 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 A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Cha ...

, 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. Like some other metal difluorides, CoF₂ crystallizes in the

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at visib ...

structure, which features octahedral Co centers and planar fluorides.

Preparation

Cobalt(II) fluoride can be prepared from anhydrous cobalt(II) chloride or cobalt(II) oxide in a stream of

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock ...

: :CoCl₂ + 2HF → CoF₂ + 2HCl :CoO + 2HF → CoF₂ + H₂O It is produced in the reaction of cobalt (III) fluoride with water. The

tetrahydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was unders ...

cobalt(II) fluoride is formed by dissolving cobalt(II) in hydrofluoric acid. The anhydrous fluoride can be extracted from this by

dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

. Other synthesis can occur at higher temperatures. It has been shown that at 500 °C

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...

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.

Analysis

To analyze 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

spectrophotometry Spectrophotometry is a branch of electromagnetic spectroscopy concerned with the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry uses photometers, known as sp ...

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 In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system ( ...

Chemical Properties

CoF₂ is a weak

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

. 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.

References

External links

National Pollutant Inventory - Cobalt fact sheet
* ttp://www.americanelements.com/cof.html {{fluorine compounds Fluorides Metal halides Cobalt(II) compounds