COBALT CHLORIDE (COCL2 (: STRUCTURE, NOMENCLATURE, PROPERTIES - CHEMISTRY - 2025

The cobalt chloride or cobalt chloride (II) is an inorganic solid formed by the union of cobalt metal in the +2 oxidation state with chloride ion. Its chemical formula is CoCl ₂.

CoCl ₂ is a crystalline solid that when in its hydrated form is red-violet in color. Gently heating it and removing the water of hydration turns blue. These color changes are due to your coordinating number changing.

Hydrated cobalt chloride crystals. Chemicalinterest. Source: Wikimedia Commons.

In the past it has been used to treat certain types of anemia, but it has been found that it can cause heart problems, deafness, gastrointestinal problems, poor thyroid function, and atherosclerosis. For these reasons it stopped being used and is still under study.

CoCl ₂ is used to speed up various chemical reactions. Its hexahydrate form in solution is used as a reference for certain chemical analyzes.

It is used to mimic hypoxia or low oxygen concentration in certain biological or medical-scientific research experiences. It has also been used to improve some mechanical properties of polymers.

Structure

Cobalt (II) chloride is made up of a cobalt atom in its +2 oxidation state and two Cl ^- chloride anions.

The electron configuration of the Co ²⁺ cation is:

1s ², 2s ² 2p ⁶, 3s ² 3p ⁶ 3d ⁷, 4s ⁰, because it has lost the 2 electrons from the 4s shell.

The electronic structure of the Cl ^- anion is:

1s ², 2s ² 2p ⁶, 3s ² 3p ⁶, because it has gained an electron in the 3p shell.

Nomenclature

-Cobalt (II) chloride

-Cobalt chloride

-Cobalt dichloride

-Dichlorocobalt

-Muriate of cobalt

-CoCl ₂: anhydrous cobalt chloride (without water of hydration)

-CoCl _{2 •} 2H ₂ O: cobalt chloride dihydrate

-CoCl _{2 •} 6H ₂ O: cobalt chloride hexahydrate

Properties

Physical state

Crystalline solid whose color depends on the degree of hydration.

Anhydrous CoCl ₂: pale blue

Anhydrous cobaltous chloride. W. Oelen. Source: Wikimedia Commons.

CoCl _{2 •} 2H ₂ O: violet

CoCl _{2 •} 6H ₂ O: red-purple or pink

Hydrated cobalt chloride. W. Oelen. Source: Wikimedia Commons.

Molecular weight

CoCl ₂: 129.84 g / mol

CoCl _{2 •} 2H ₂ O: 165.87 g / mol

CoCl _{2 •} 6H ₂ O: 237.93 g / mol

Melting point

CoCl ₂: 735 ºC

CoCl _{2 •} 6H ₂ O: 86 ºC

Boiling point

CoCl ₂: 1053 ºC

Density

CoCl ₂: 3.356 g / cm ³

CoCl _{2 •} 2H ₂ O: 2.477 g / cm ³

CoCl _{2 •} 6H ₂ O: 1.924 g / cm ³

Solubility

CoCl ₂: 45 g / 100 mL of water

CoCl _{2 •} 2H ₂ O: 76 g / 100mL of water

CoCl _{2 •} 6H ₂ O: 93 g / 100mL of water

Other properties

Cobalt (II) chloride hexahydrate is pink, but when slightly heated it turns blue as it loses water. If the anhydrous CoCl ₂ is left in a humid atmosphere, it turns pink.

The color of the cobalt ion depends on the coordination number, that is, on the groups attached to the Co ²⁺ ion. A coordination number of 6 corresponds to pink compounds and a coordination number of 4 results in blue compounds.

When CoCl ₂ is in aqueous solution, the following equilibrium occurs:

Co (H ₂ O) ₆ ⁺⁺ + 4 Cl ^- ⇔ CoCl ₄ ^- + 6 H ₂ O

When the equilibrium shifts towards Co (H ₂ O) ₆ ⁺⁺ the solution is red, while when it shifts towards CoCl ₄ ^- the solution is blue.

Applications

Treatment of special cases of anemia

Cobalt chloride was widely used since the 1930s for the treatment of certain types of anemia, both in Europe and in the USA.

Its oral administration favors an increase in hemoglobin, erythrocyte count and hematocrit. The response is proportional to the dose used. This is because it exerts a stimulating action on the bone marrow.

Illustration of red blood cells in the blood. Author: Gerd Altmann. Source: Pixabay.

However, its use was discontinued due to side effects such as gastrointestinal upset, cardiomyopathies, nerve deafness, and abnormal thyroid function.

Despite such drawbacks, in 1975 it was successfully tested in kidney failure patients whose anemia is caused by repeated blood loss due to dialysis.

Hematocrit and red cell volume were found to increase in these patients indicating stimulation of erythropoiesis or red blood cell formation.

For this reason, cobalt chloride was thought to be of value in hemodialysis patients in whom other ways to alleviate anemia have failed.

However, it was later observed that high levels of Co ²⁺ in the blood were related to atherosclerosis, which is why more studies are currently being carried out to determine its potential benefits or harm for this type of patients.

In catalysis of chemical reactions

Cobalt chloride has application in the acceleration of certain chemical reactions.

For example, in the esterification of unsaturated compounds of high molecular weight, the use of CoCl ₂ as a catalyst leads to obtaining the desired product without the formation of collateral derivatives.

Increasing the CoCl ₂ concentration and temperature increases the rate of the reaction.

As a standard in chemical analysis

CoCl _{2 •} 6H ₂ O is used as a standard or color reference in some analysis methods of the American Public Health Association, or APHA (American Public Health Association).

Cobalt chloride colored solutions in various equilibria with hydrochloric acid HCl. Chemicalinterest. Source: Wikimedia Commons.

In ischemia research

Ischemia is the decrease in blood flow in a part of the body and remedies are continually being investigated to avoid it or prevent its consequences.

It has been found that CoCl ₂ can induce apoptosis or cell death of cancer model cells.

CoCl ₂ triggers the production of reactive oxygen species in such cancer model cells, which leads to their death via apoptosis. It is said to induce a hypoxia-mimicking response.

This result indicates that CoCl ₂ may help to investigate the molecular mechanism in hypoxia-associated cell death and to find remedies against ischemia.

As a model to mimic hypoxia in biological and medical research

Hypoxia is the decrease in available oxygen necessary for the function of the cell. CoCl ₂ is one of the compounds used in medical-scientific and biological research to induce chemical hypoxia.

The mechanism of action of CoCl ₂ in cells gives the researcher a longer time to manipulate and analyze their samples under hypoxic conditions.

Its use is considered a reliable method, since it allows experiments under low oxygen conditions without the use of special cameras.

However, the interpretation of the results obtained must be carefully reviewed, as the researcher must ensure that cobalt has no other effects on the function of the cells under study apart from mimicking hypoxia.

In research on the use of water as a source of hydrogen

Cobalt chloride has been studied as a catalyst in the investigation of obtaining hydrogen from water using solar energy.

The Co ²⁺ ion can act as a homogeneous catalyst during the photochemical oxidation of water under acidic conditions (presence of acid HCl and pH 3) to avoid precipitation.

This type of study sheds light and helps in the search for clean energy and sustainable solar energy.

To improve the mechanical properties of polymers

Some researchers incorporated CoCl ₂ into acrylonitrile-butadiene-styrene, or ABS (Acrylonitrile-Butadiene-Styrene) polymer blends, with nitrile-butadiene rubber, or NBR (Nitrile Butadiene Rubber).

The CoCl _{2 was} incorporated into the ABS-NBR mixture and the whole was hot compressed. The results indicate that the NBR was uniformly dispersed in the ABS and that the CoCl ₂ tends to be distributed in the NBR phase.

The coordination reaction between the Co ²⁺ ' cations and the -CN groups has a positive impact on the mechanical properties. Increasing the CoCl ₂ content increases the tensile strength and the ease of bending.

However, a decrease in thermal stability and problems with the absorption of water from CoCl _{2 were} observed, so this type of mixture will continue to be studied.

Harmful or lethal administration to horses

CoCl ₂ has been used in very small amounts in horse feed.

Cobalt is an important element (in traces) for horse nutrition, since it is used by bacteria in their intestinal tract to synthesize vitamin B12 (cobalamin).

However, recent studies (2019) indicate that cobalt supplementation in horse feed is neither useful nor necessary and that it can be potentially lethal for these animals.

Horses do not require additional cobalt chloride supplementation. Author: Alexas Fotos. Source: Pixabay.

References

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