Cobalt(II) chloride

Cobalt(II) chloride hexahydrate (with six water molecules attached)

Cobalt(II) chloride anhydrous (with no water molecules attached)

Cobalt(II) chloride, also known as cobaltous chloride and cobalt dichloride, is a chemical compound. It contains cobalt in its +2 oxidation state. Its chemical formula is CoCl₂. It contains cobalt and chloride ions.

Properties

Cobalt(II) chloride is normally found in the red (or pink) form. The red form has water in it. It can be heated to turn it into the blue form, without water. The blue form will absorb water from the air and turn red again.

Cobalt(II) chloride reacted with hydrochloric acid. The pink form is just cobalt chloride. The blue form is the color that it gives with some hydrochloric acid. The green form is cobalt chloride reacted with a lot of hydrochloric acid.

A different blue form is made when cobalt(II) chloride is reacted with a chemical compound that has chloride in it. Hydrochloric acid works the best, but sodium chloride can be used too. When it is heated, it turns more blue than when it is cooled. See and for an example. Cobalt chloride can be used to test for chloride ions in this way.

It can be oxidized to cobalt(III) compounds, although cobalt(III) chloride does not exist. If it is made, it just drops a Cl from CoCl₃, making CoCl₂ (cobalt(II) chloride) again.

Preparation

The anhydrous (without water) blue form can be made by reacting cobalt with chlorine. The hydrated (with water) red form can be made by reacting cobalt(II) oxide or cobalt(II) hydroxide with hydrochloric acid.

Uses

It is used to place cobalt into other chemical compounds. It can be used to make other cobalt compounds. It is the most common cobalt compound in the lab.

Safety

It is a weak oxidizing agent, too weak to ignite things. Cobalt compounds are toxic in large quantities, like any other transition metal compounds. They are not toxic like lead or mercury compounds, though.

See also

• Cobalt(III) oxide
• Cobalt(II) sulfate