Cobalt

Sheet of cobalt metal

Cobalt (chemical symbol Co) is a chemical element. It has an atomic number of 27 and an atomic mass of about 59. It is a metal.

Properties

Cobalt(II) chloride with water

Cobalt(II) chloride without water

Cobalt is a transition metal. It is shiny and conducts electricity. It is magnetic. It is a hard metal. It is moderately reactive. Iron is more reactive and copper is less reactive. It dissolves slowly in acids. This reaction makes hydrogen and a salt of cobalt. Cobalt is normally in its +2 oxidation state as an ion. Some chemical compounds contain cobalt ions in its +4 oxidation state. Cobalt(II) chloride is one of the most common cobalt compounds. Many cobalt compounds are blue or pink. One of them is black.

Occurrence and preparation

Cobalt is too reactive to occur pure in the earth. It is found in certain minerals. It is found with copper and nickel deposits. Normally the three metals are bonded to arsenic and sulfur. It is found as a byproduct (left over substance) when copper and nickel are produced. It is made by reaction with the sludge from copper and nickel processing.

Uses

Glass colored with cobalt

Cobalt is used in some types of steel. It hardens the steel. It is also used to make very strong tough alloys. These alloys are known as superalloys. Some cobalt compounds are used in the lithium-ion battery. Cobalt compounds were used as an artificial food coloring until 1971. It was discovered that it has harmful effects. It is used to make glass blue. It is also used as a catalyst. It is also used in some medicines.

The human body needs small amounts of cobalt for certain vitamins. Cobalt compounds are used to stop cyanide from poisoning the body.

Safety

Cobalt compounds are needed in small amounts, but they are toxic in large quantities. Sometimes cobalt compounds were added to beer and poisoned people that drank it. It can make skin irritation when touched.