Cobalt(II) fluoride

Cobalt(II) fluoride
Cobalt(II) fluoride
Identifiers
CAS number 10026-17-2
PubChem 24854139
ChemSpider 23205 YesY
EC number 233-061-9
RTECS number GG0770000
Jmol-3D images Image 1
Properties
Molecular formula CoF2
Molar mass 96.93 g/mol
Appearance Red crystalline solid
Density 4.46 g/cm3 (anhydrous)
2.22 g/cm3 (trihydrate)
Melting point

1217 °C, 1490 K, 2223 °F

Boiling point

1400 °C, 1673 K, 2552 °F

Solubility in water Insoluble
Hazards
NFPA 704
NFPA 704.svg
0
3
2
LD50 oral (rat): 150 mg/kg
Related compounds
Other anions cobalt(II) oxide, cobalt(II) chloride
Other cations iron(II) fluoride, nickel(II) fluoride
Related compounds cobalt trifluoride
 YesY fluoride (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Cobalt(II) fluoride is a chemical compound with the formula (CoF2). It is a pink crystalline solid compound.[1][2] 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.

Contents

Preparation

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

CoCl2 + 2HF → CoF2 + 2HCl
CoO + 2HF → CoF2 + H2 O

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.[3]

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[citation needed], 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 spectrophotometry 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%.

Chemical Properties

CoF2 is a weak Lewis acid. 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

  1. ^ Pradyot Patnaik (2002), Handbook of Inorganic Chemicals, McGraw-Hill Professional, ISBN 9780070494398, http://books.google.com/?id=Xqj-TTzkvTEC&pg=PA241&lpg=PA241&dq=%22Cobalt(II)+fluoride%22 
  2. ^ Pashkevich, D. S. Radchenko, S. M. Mukhortov, D. A., "Article title Heat Exchange between Cobalt(II) Fluoride Powder and the Wall of Rotating Cylinder", Russian Journal of Applied Chemistry (Consultants Bureau), ISSN 1070-4272, http://www.maik.rssi.ru/abstract/rjapchem/97/rjapchem1447_abstract.pdf 
  3. ^ J.C. Bailar (1973), Comprehensive Inorganic Chemistry, Pergoamon 

External links



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См. также в других словарях:

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  • cobalt fluoride — noun : either of two fluorides of cobalt: a. : the difluoride CoF2 obtained as a rose colored granular powder called also cobaltous fluoride b. : the trifluoride CoF3 obtained as a brown crystalline material and used as a carrier of fluorine in… …   Useful english dictionary


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