Cobalt

Cobalt (paints, and varnishes.

Notable characteristics

Cobalt metal is a silver or gray Mohs scale of mineral hardness.^{[citation needed]}

Common oxidation states of cobalt include +2 and +3, although compounds with oxidation state +1 are also well developed.

Isotopes

Main article: Isotopes of cobalt

Naturally occurring cobalt is "monoisotopic", i.e. only one radioactive isotopes have half-lives that are less than 18 hours and the majority of these have half-lives that are less than 1 second. This element also has 4 meta states, all of which have half-lives less than 15 minutes.

The isotopes of cobalt range in isotopes.

Cobalt radioisotopes in medicine

radioactive, and so cobalt machines have fallen from favor in the Western world where linacs are common.

Cobalt-57 (Co-57 or ⁵⁷Co) is a radioactive metal that is used in medical tests; it is used as a radiolabel for vitamin B₁₂ uptake. It is useful for the Schilling's test.^[1]

Industrial uses for radioactive isotopes

Cobalt-60 (Co-60 or ⁶⁰Co) is useful as a neutrons in a reactor for a given time. It is used for

• sterilization of medical supplies, and medical waste;
• pasteurization);
• industrial radiography (e.g., weld integrity radiographs);
• density measurements (e.g., concrete density measurements); and
• tank fill height switches.

Cobalt-59 is used as a source in Mössbauer spectroscopy.

Applications

• Alloys, such as
  • Superalloys, for parts in gas turbine aircraft engines.
  • Corrosion- and wear-resistant alloys.
  • High speed steels.
  • Cemented diamond tools.
• Magnets and magnetic recording media.
  • Alnico magnets.
  • Samarium-cobalt magnets.
• oxidation.
• oxidation.
• Drying agents for paints, varnishes, and inks.
• Ground coats for porcelain enamels.
• Pigments (cobalt blue and cobalt green).

• battery electrodes.
• Steel-belted radial tires.
• Purification of histidine-tagged fusion proteins in biotechnology applications.

History

Cobalt compounds have been used for centuries to impart a rich blue color to glass, glazes, and ceramics. Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of Pompeii (destroyed AD 79), and in China dating from the Tang dynasty (AD 618–907) and the Ming dynasty (AD 1368–1644)^[2]. Cobalt glass ingots have been recovered from shipwrecks dating to the time of the Minoans^{[citation needed]} (BC 2700-1450).

Swedish chemist George Brandt (1694–1768) is credited with isolating cobalt in 1735. He was able to show that cobalt was the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt.

During the 19th century, cobalt blue was produced at the Norwegian Blaafarveværket (70-80% of world production), led by the Prussian industrialist Benjamin Wegner.

In 1938, John Livingood and cobalt-60.

The word cobalt is derived from the German kobalt, from kobold meaning "goblin", a term used for the ore of cobalt by miners. The first attempts at smelting the cobalt ores to produce cobalt metal failed, yielding cobalt(II) oxide instead; not only that, but because of cobalt's curious affinity for arsenic, the primary ores of cobalt always contain arsenic, and upon smelting the arsenic oxidized into the highly toxic As₄O₆, which was breathed in by workers.

Biological role

Cobalt in small amounts is essential to many living organisms, including humans. Having 0.13 to 0.30 mg/kg of cobalt in soils markedly improves the health of grazing animals. Cobalt is a central component of the vitamin B₁₂.

Occurrence

      Cobalt is not found as a skutterudite.

In 2005, the Democratic Republic of the Congo was the top producer of cobalt with almost 40% world share followed by Canada, Zambia, Russia, Brazil and Cuba, reports the British Geological Survey.

see also Category:Cobalt minerals

Compounds

There is a wide variety of cobalt compounds. The +2 and +3 hydrolyzed in water), all compounds containing cobalt in the +3 oxidation state are stabilized by complex ion formation.

see also Category:Cobalt compounds

Precautions

Powdered cobalt in metal form is a fire hazard.

Cobalt compounds should be handled with care due to cobalt's slight toxicity.

gamma ray emitter. Acute high-dose exposures to the gamma emissions, such as can occur when irradiation equipment is inadvertently diverted into scrap, can cause severe burns and death. Extended exposures increase the risk of morbidity or mortality from cancer.^[3]

Nuclear weapon designs could intentionally incorporate ⁵⁹Co, some of which would be activated in a nuclear explosion to produce ⁶⁰Co. The ⁶⁰Co, dispersed as cobalt bomb, once predicted by physicist Leó Szilárd as being capable of wiping out all life on earth.

Cobalt in Popular Culture

- In the 1989 sequel Ghostbusters II, Egon Spengler replies to Ray's question about the connection between Vigo and the slime with the rhetorical: "Is the atomic weight of Cobalt 58.8?"

References & notes

• Los Alamos National Laboratory: Cobalt

1. ^ JPNM Physics Isotopes
2. ^ Encyclopedia Britannica Online.
3. ^ The Juarez accident