Cobalt is a chemical element with the symbol Co and the atomic number 27. It readily forms compounds with other elements and compounds. When it is extracted from naturally occurring compounds via reductive smelting, it is a hard, shiny, sliver-gray metal.
The name comes from the German word “kobold” which mean “goblin.” Miners were familiar with ores that were poor in metals that they called goblin ore partly because of the deadly arsenic fumes given off when heated. The minerals in such ores were used since ancient times as a pigment for blue paint. Most of the cobalt ore mined in the world today is a byproduct of copper and nickel mining in the Democratic Republic of Congo and Zambia in Africa.
Today cobalt is used to create high-strength alloys which are wear-resistant and magnetic. Silicate and aluminate compounds of cobalt are used to impart a deep blue color to glass, ceramics, inks, paints and varnishes.
Cobalt is present in living cells. The cobalt atom forms the active center of certain coenzymes called cobalamins. The vitamin B12 is an example of such cobalamins. Cobalt is a necessary trace dietary mineral for all living creatures.
Naturally occurring cobalt contains the stable isotope with an atomic weight of 59 which is the only stable isotope. There are a total of 28 radioactive isotopes that range from atomic weight of 47 to 73. They vary Co-51 with a half-life of 200 billionth of a second to Co-60 with a half-life of 5.27 years.
Cobalt-60 is created by bombarding the stable Co-59 with slow neutrons in CANDU reactors or from californium-252. It undergoes beta decay to Nickel-70 which then gives off gamma radiation to achieve a stable state. It is the emission of gamma rays that makes Co-60 a useful isotope. It is used as a tracer for chemical reactions, sterilization of medical equipment, a source of radiation for medical radiotherapy, a radiation source for industrial radiography, a radiation source for leveling devices and thickness gauges, a radiation source to sterilize food and blood and a radiation source for general laboratory use.
One of the problems with the use of Co-60 is the fact that the solid form can disintegrate into a powder which can be inhaled and cause biological damage. This makes the handling of devices employing Co-60 more dangerous. Its use in many applications as a gamma ray source has been declining. Improper disposal of medical equipment containing Co-60 as scrap metal led to radioactivity appearing in iron produced by smelting the contaminated scrap.
Cobalt-57 is made in cyclotrons by the irradiation of iron. It has a half-life of 271 days and it decays by electron capture to Iron-57 which emits gamma radiation to achieve a stable state. It is used in medicine as a tracer for the metabolization of vitamin B12.
Cobalt 60 cancer therapy machine:
