Element Cobalt, Co, Transition Metal
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Cobalt History
Cobalt compounds have been known for millennia. Cobalt glass ingots have been recovered from Egyptian ancientries such as jar dating to the 15th century B.C., in coloring of which cobalt salts had been used, as well as in the cobalt-contained glassbricks. Ancient Assyrians and Babylonians used to produce blue paints which were used for ceramics glazing. Perhaps bismuth- and cobalt-contained sapphire was the initial material from which the names of blue paints came.
Swedish chemist, director of the chemical laboratory of the Council of Mines, Stockholm George Brandt (1694-1768) is credited with isolating and describing cobalt in 1735. As he wrote in his dissertation entitled "About half-metals": "As there are six kinds of metals, so I have also shown with reliable experiments... that there are also six kinds of half-metals: a new half-metal, namely Cobalt regulus". He showed that cobalt was the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt.
According to some sources, pure cobalt was separated by Berzelius.
Cobalt Occurrence
The cobalt abundance in lithosphere is 1.8x10-3 mass %. It migrates in magmas of the Earth's crust and in hot and cold waters. Due to the process of magmatic differentiation cobalt is deposited mostly in upper mantle. Magmatic processes are also responsible for so-called segregation deposits of cobalt ores. In hydrothermal deposits cobalt is associated with Nickel, Arsenic, Sulphur and Copper. In total approximately 30 cobalt ores are known.
Cobalt disperses in biosphere; however some plants are able to concentrate it participating in origin of cobalt deposits. In upper layers of Earth crust a distinctive differentiation of cobalt concentration may be observed: 2x10-3% in slates, 3x10-5% in sandstones, 1x10-5 in limestone. Sand soils of forest areas contain lower amount of cobalt. Surface waters are also poor by cobalt: the ocean concentration does not exceed 5x10-8%. Being very poor water migrant cobalt is easily transferred to sedimentary rocks in which it is absorbed by manganese hydroxides, clays, and other highly dispersed adsorbents.
Cobalt is a microelement, which means that it permanently occurs in biological tissues. Some terrestrial plants and seaweeds are able to concentrate cobalt. Being a constituent part of vitamin B12, also called cobalamin, cobalt participates in the most important functions such as haematogenesis, in processes in neurosystem, in liver, etc. Cobalt is important for enzymatic processes of fixation of air nitrogen by legume bacteria. An average human body (70 kg) contains approximately 14 mg of cobalt.
Cobalt Neighbours
D. Mendeleev Periodic Table | |