Cobalt

Cobalt

Discovery of Cobalt

Cobalt compounds have long been used in the production of blue glass and ceramics. This element was first isolated in 1735 by the Swedish chemist George Brandt. He showed that the elemental cobalt causes the blue color of glass instead of bismuth, as previously envisioned.

Cobalt ( Co ) – a chemical element, ferromagnetic metal of Group 9 ( VIIIb ) of the periodic table, used especially for heat-resistant and magnetic alloys.

The name cobalt comes from the German word 'kobold,' which means goblin or elf. Cobalt has been found in Egyptian statuettes and Persian necklace beads dating from the third millennium BCE, in glass discovered in the Pompeii ruins, and in Chinese blue porcelain dating from the Tang dynasty ( 618–907 CE ) and the Ming dynasty ( 1368–1644 ). The name kobold was first applied to ores supposed to contain copper but were later discovered to be toxic arsenic-bearing cobalt ores in the 16th century. The presence of cobalt, according to Brandt ( 1742 ), caused the blue color of those ores.

Characteristics

Cobalt is a bluish-white metal that is shiny, hard, and brittle. It has a ferromagnetic property. Chemically, the metal is active, producing a variety of compounds. Cobalt is the magnetic element that remains magnetic at the highest temperature of all the magnetic elements ( it has a Curie point of 1121oC ). Cobalt ( Co ) is a chemical element that belongs to Group 9 ( VIIIb ) of the periodic table and is utilized in heat-resistant and magnetic alloys.

Occurrence, Features, and Usage

Despite its widespread distribution, cobalt accounts for only 0.001% of the Earth's crust. It can be found in small quantities in terrestrial and meteoritic native nickel-iron, in the Sun's and stellar atmospheres, and in natural waters, ferromanganese crusts deep beneath the oceans, in soils, in plants and animals, and in minerals like cobaltite, linnaeite, skutterudite, smaltite, heterogenite, and erythrite. Cobalt is a trace metal that is required for the feeding of ruminants ( cattle, sheep ) and the development of human red blood cells in the form of vitamin B12, which is the only vitamin known to include such a heavy element.

Cobalt ore is rarely mined for its cobalt content, with a few exceptions. Rather, it is frequently collected as a by-product from the mining of ores containing traces of cobalt, such as iron, nickel, copper, silver, manganese, zinc, and arsenic. Concentrating and extracting cobalt from these ores requires extensive processing. The Democratic Republic of the Congo ( DRC ), China, Canada, and Russia were the world's main producers of mined cobalt by the second decade of the twenty-first century. China, on the other hand, was the leading producer of refined cobalt, importing massive amounts of cobalt mining resources from the DRC.

Cobalt is a silver-white metal with a bluish tinge when polished. The hexagonal close-packed form, stable below 417 °C (783 °F), and the face-centered cubic structure, stable at high temperatures, are both known allotropes. It is ferromagnetic up to 1,121 °C (2,050 °F), the highest known Curie point of any metal or alloy, and may find application where magnetic properties are needed at elevated temperatures.

At normal temperatures, cobalt is one of three ferromagnetic metals. It dissolves slowly in dilute mineral acids and does not react with hydrogen or nitrogen immediately, but will react with carbon, phosphorus, or sulfur when heated. At high temperatures, cobalt is attacked by oxygen and water vapors, resulting in the formation of cobaltous oxide, CoO (with the metal in the +2 state).

Natural cobalt is entirely composed of the stable isotope cobalt-59, from which the longest-lived artificial radioactive isotope cobalt-60 (with a half-life of 5.3 years) is made by neutron irradiation in a nuclear reactor. In the inspection of industrial materials, gamma radiation from cobalt-60 has been utilized instead of X-rays or alpha rays from radium to reveal interior structures, fractures, or foreign items. It has also been utilized as a radioactive tracer in cancer therapy, sterilization investigations, and biology and industry.

The majority of cobalt is used in specific alloys. Magnetic alloys, such as Alnicos for permanent magnets, consume a significant portion of global output. For alloys that retain their qualities at high temperatures and superalloys that are used near their melting points, large volumes are used (where steels would become too soft). Hard-facing alloys, tool steels, low-expansion alloys (for glass-to-metal closures), and constant-modulus (elastic) alloys are all made with cobalt (for precision hairsprings). The most suitable matrix for cemented carbides is cobalt.

Cobalt that has been finely separated spontaneously burns. Larger particles are rather inert in air, although substantial oxidation occurs above 300 °C (570 °F).

Abundance and Isotopes

Abundance earth’s crust: 25 parts per million by weight, 8 parts per million by moles.

Abundance solar system: 4 parts per million by weight, 0.7 parts per million by moles.

Source: In nature, cobalt does not exist as a free element. Mineral ores contain it. Cobaltite (CoAsS), erythrite (hydrated arsenate of cobalt), glaucodot (Co,Fe)AsS, and skutterudite (Co,Ni)As3 are the most common cobalt ores. Cobalt is typically mined as a by-product of nickel and copper extraction.

Isotopes: Cobalt has 22 isotopes with known half-lives, ranging in mass from 50 to 72. The only stable isotope of cobalt found in nature is 59Co.