Cobalt is a
chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with symbol
Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray
metalA metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
.
Cobalt-based blue pigments have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was later thought by alchemists to be due to the known metal
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
. Miners had long used the name
koboldThe kobold is a sprite stemming from Germanic mythology and surviving into modern times in German folklore. Although usually invisible, a kobold can materialise in the form of an animal, fire, a human being, and a candle. The most common depictions of kobolds show them as humanlike figures the size...
ore (German for
goblin ore) for some of the blue-pigment producing minerals; they were named because they were poor in known metals and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the
kobold.
Nowadays, some cobalt is produced specifically from various metallic-lustered ores, for example
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
(CoAsS), but the main source of the element is as a by-product of
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
and
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
mining. The copper belt in the
Democratic Republic of the CongoThe Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
and
ZambiaZambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
yields most of the cobalt metal mined worldwide.
Cobalt is used in the preparation of
magneticMagnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
, wear-resistant and high-strength
alloyAn alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s. Cobalt silicate and cobalt(II) aluminate (CoAl
2O
4,
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
) give a distinctive deep blue color to
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
,
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
, ceramics,
inkInk is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...
s,
paintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
s and
varnishVarnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
es. Cobalt occurs naturally as only one stable isotope, cobalt-59.
Cobalt-60Cobalt-60, , is a synthetic radioactive isotope of cobalt. Due to its half-life of 5.27 years, is not found in nature. It is produced artificially by neutron activation of . decays by beta decay to the stable isotope nickel-60...
is a commercially important radioisotope, used as a
radioactive tracerA radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...
and in the production of
gamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s.
Cobalt is the active center of coenzymes called cobalamins, the most common example of which is
vitamin B12Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
. As such it is an essential trace
dietary mineralDietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
for all animals. Cobalt in inorganic form is also an active nutrient for bacteria,
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and fungi.
Characteristics
Cobalt is a
ferromagneticFerromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished...
metal with a
specific gravitySpecific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 8.9. Pure cobalt is not found in nature, but compounds of cobalt are common. Small amounts of it are found in most rocks, soil, plants and animals. The Curie temperature is 1115 °C and the magnetic moment is 1.6–1.7
Bohr magnetons per
atomThe atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
. In nature, it is frequently associated with nickel, and both are characteristic minor components of meteoric iron. Cobalt has a
relative permeabilityIn electromagnetism, permeability is the measure of the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field. Magnetic permeability is typically...
two thirds that of
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. Metallic cobalt occurs as two crystallographic structures: hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the energy difference is so small that random intergrowth of the two is common.
Cobalt is a weakly reducing metal that is protected from oxidation by a
passivatingPassivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...
oxide film. It is attacked by halogens and sulfur. Heating in oxygen produces
Co3O4Cobalt oxide is inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid...
which loses oxygen at 900 °C to give the
monoxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
CoO.
Compounds
Common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +4 are also known. A common oxidation state for simple compounds is +2. Cobalt(II) salts form the red-pink [Co(H
2O)
6]
2+ complex in aqueous solution. Addition of chloride gives the intensely blue .
Oxygen and chalcogen compounds
Several
oxideAn oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s of cobalt are known. Green
cobalt(II) oxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
(CoO) has
rocksaltIn crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....
structure. It is readily oxidized with water and oxygen to brown cobalt(III) hydroxide (Co(OH)
3). At temperatures of 600–700 °C, CoO oxidizes to the blue
cobalt(II,III) oxideCobalt oxide is inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid...
(Co
3O
4), which has a
spinelSpinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
structure. Black
cobalt(III) oxideCobalt oxide is the inorganic compound with the formula Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co salts such as cobalt nitrate with an aqueous solution of sodium hypochlorite gives a...
(Co
2O
3) is also known. Cobalt oxides are antiferromagnetic at low
temperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
: CoO (
Neel temperatureThe Néel temperature or magnetic ordering temperature , TN, is the temperature above which an antiferromagnetic material becomes paramagnetic—that is, the thermal energy becomes large enough to destroy the macroscopic magnetic ordering within the material....
291 K) and Co
3O
4 (Neel temperature: 40 K), which is analogous to
magnetiteMagnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
(Fe
3O
4), with a mixture of +2 and +3 oxidation states.
The principal
chalcogenThe chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...
ides of cobalt include the black cobalt(II) sulfides, CoS
2, which adopts a
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
-like structure, and Co
2S
3.
PentlanditePentlandite is an iron-nickel sulfide, 9S8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt.Pentlandite forms isometric crystals, but is normally found in massive granular aggregates. It is brittle with a hardness of 3.5 - 4 and specific gravity of 4.6 - 5.0 and...
(Co
9S
8) is metal-rich.
Halides
The four dihalides of cobalt(II) are known:
cobalt(II) fluorideCobalt fluoride is a chemical compound with the formula . It is a pink crystalline solid compound. The formula is given for both the red tetragonal crystal, , and the tetrahydrate red orthogonal crystal, . CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it...
(CoF
2, pink),
cobalt(II) chlorideCobalt chloride is an inorganic compound of cobalt and chloride, with the formula CoCl2. It is usually supplied as the hexahydrate CoCl2·6H2O, which is one of the most commonly used cobalt compounds in the laboratory. The hexahydrate is deep purple in color, whereas the anhydrous form is sky blue...
(CoCl
2, blue),
cobalt(II) bromideCobalt bromide is an inorganic compound used primarily as a catalyst in some processes.-Properties:When anhydrous, cobalt bromide appears as green crystals. The hexahydrate loses four waters of crystallization molecules at 100°C forming the dihydrate:Further heating to 130°C Produces the anhydrous...
(CoBr
2, green),
cobalt(II) iodideCobalt iodide or cobaltous iodide is the inorganic compound composed with the formula Co I2. The two forms of CoI2 and the hydrated form are the principal iodides of cobalt.-Synthesis and structure:...
(CoI
2, blue-black). These halides exist as anhydrous and hydrates. Whereas the anhydrous dichloride is blue, the hydrate is red.
The reduction potential for the reaction
- + →
is +1.92 V, beyond that for
chlorineChlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
to chloride, +1.36 V. As a consequence cobalt(III) and chloride would result in the cobalt(III) being reduced to cobalt(II). Because the reduction potential for fluorine to fluoride is so high, +2.87 V, cobalt(III) fluoride is one of the few simple stable cobalt(III) compounds. Cobalt(III) fluoride, which is used in some fluorination reactions, reacts vigorously with water.
Coordination compounds
As for all metals, molecular compounds of cobalt are classified as coordination complexes, that is molecules or ions that contain cobalt linked to several
ligandIn coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s. The principles of
electronegativityElectronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
and
hardness–softnessThe HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
of a series of ligands can be used to explain the usual oxidation state of the cobalt. For example Co
+3 complexes tend to have
ammineIn coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelled with a single "m"...
ligands. As phosphorus is softer than nitrogen, phosphine ligands tend to feature the
softerThe HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
Co
2+ and Co
+, an example being tris(triphenylphosphine)cobalt(I) chloride ((P(C
6H
5)
3)
3CoCl). The more electronegative (and harder) oxide and fluoride can stabilize Co
4+ derivatives, e.g. caesium hexafluorocobaltate (Cs
2CoF
6) and potassium percobaltate (K
3CoO
4).
Alfred WernerAlfred Werner was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry...
, a Nobel-prize winning pioneer in coordination chemistry, worked with compounds of
empirical formulaIn chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic...
CoCl
3(NH
3)
6. One of the isomers determined was
cobalt(III) hexammine chlorideHexamminecobalt chloride is the chemical compound with the formula [Co6]Cl3. This coordination compound is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner. This salt consists of [Co6]3+ trications with three Cl− anions...
. This coordination complex, a "typical" Werner-type complex, consists of a central cobalt atom coordinated by six
ammineIn coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelled with a single "m"...
ligands orthogonal to each other and three
chlorideThe chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
counteranions. Using chelating ethylenediamine ligands in place of ammonia gives
tris(ethylenediamine)cobalt(III) chlorideTriscobalt chloride is a coordination complex with the formula [Co3]Cl3 . This complex was important in the history of coordination chemistry because of its stability and its stereochemistry. Many different salts have been described...
([Co(en)
3]Cl), which was one of the first coordination complexes that was resolved into
optical isomersA chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
. The complex exists as both either right- or left-handed forms of a "three-bladed propeller". This complex was first isolated by Werner as yellow-gold needle-like crystals.
Organometallic compounds
CobaltoceneCobaltocene, known also as biscobalt or even "bis Cp cobalt", is an organocobalt compound with the formula Co2. It is a dark purple solid that sublimes readily slightly above room temperature. Cobaltocene was discovered shortly after ferrocene, the first metallocene...
is a structural analog to
ferroceneFerrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds...
, where cobalt substitutes for iron. Cobaltocene is sensitive to oxidation, much more than ferrocene. Cobalt carbonyl (Co
2(CO)
8) is a
catalystCatalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
in
carbonylationCarbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry.-Organic chemistry:...
reactions.
Vitamin B12Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
(see below) is an organometallic compound found in nature and is the only
vitaminA vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
to contain a metal atom.
Isotopes
59Co is the only stable cobalt
isotopeIsotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
and the only isotope to exist in nature. 22 radioisotopes have been characterized with the most stable being
60Co with a
half-lifeHalf-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 5.2714 years,
57Co with a half-life of 271.79 days,
56Co with a half-life of 77.27 days, and
58Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are shorter than 18 hours, and the majority of these are shorter than 1 second. This element also has 4 meta states, all of which have half-lives shorter than 15 minutes.
The isotopes of cobalt range in
atomic weightAtomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
from 50
uThe unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
(
50Co) to 73 u (
73Co). The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope,
59Co, is
electron captureElectron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
and the primary mode of decay for those of greater than 59 atomic mass units is
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
. The primary
decay productIn nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...
s before
59Co are element 26 (
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
) isotopes and the primary products after are element 28 (nickel) isotopes.
History
Cobalt compounds have been used for centuries to impart a rich blue color to
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
,
glazesGlaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
and
ceramicsIn art history, ceramics and ceramic art mean art objects such as figures, tiles, and tableware made from clay and other raw materials by the process of pottery. Some ceramic products are regarded as fine art, while others are regarded as decorative, industrial or applied art objects, or as...
. Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of
PompeiiThe city of Pompeii is a partially buried Roman town-city near modern Naples in the Italian region of Campania, in the territory of the comune of Pompei. Along with Herculaneum, Pompeii was destroyed and completely buried during a long catastrophic eruption of the volcano Mount Vesuvius spanning...
(destroyed in 79 AD), and in China dating from the
Tang dynastyThe Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
(618–907 AD) and the
Ming dynastyThe Ming Dynasty, also Empire of the Great Ming, was the ruling dynasty of China from 1368 to 1644, following the collapse of the Mongol-led Yuan Dynasty. The Ming, "one of the greatest eras of orderly government and social stability in human history", was the last dynasty in China ruled by ethnic...
(1368–1644 AD).
Cobalt has been used to color glass since the
Bronze AgeThe Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...
. The excavation of the
Uluburun shipwreckThe Uluburun Shipwreck is a Late Bronze Age shipwreck dated to the late 14th century BCE, discovered off Uluburun situated about 6 miles southeast of Kaş, in south-western Turkey...
yielded an ingot of blue glass, which was cast during the 14th century BC. Blue glass items from Egypt are colored with copper, iron, or cobalt. The oldest cobalt-colored glass was from the time of the
Eighteenth dynastyThe eighteenth dynasty of ancient Egypt is perhaps the best known of all the dynasties of ancient Egypt...
in
EgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
(1550–1292 BC). The location where the cobalt compounds were obtained is unknown.
The word
cobalt is derived from the German
, from
koboldThe kobold is a sprite stemming from Germanic mythology and surviving into modern times in German folklore. Although usually invisible, a kobold can materialise in the form of an animal, fire, a human being, and a candle. The most common depictions of kobolds show them as humanlike figures the size...
meaning "goblin", a superstitious term used for the
oreAn ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
of cobalt by miners. The first attempts at smelting these ores to produce metals such as copper or nickel failed, yielding simply powder (cobalt(II) oxide) instead. Also, because the primary ores of cobalt always contain
arsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, smelting the ore oxidized the arsenic content into the highly toxic and volatile arsenic oxide, which also decreased the reputation of the ore for the miners.
Swedish chemist
Georg Brandt-External links:** by Uno Boklund in: Charles C. Gillispie, ed., Dictionary of Scientific Biography , vol. 2, pages 421-422....
(1694–1768) is credited with discovering cobalt circa 1735, showing it to be a new previously unknown element different from bismuth and other traditional metals, and calling it a new "semi-metal." He was able to show that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period, during which all the known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers.
During the 19th century, a significant part of the world's production of
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
(a dye made with cobalt compounds and alumina) and
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
(
cobalt glassCobalt glass is a deep blue colored glass prepared by adding cobalt compounds to the molten glass. It is appreciated for its attractive color. It is also used as an optical filter in flame tests to filter out the yellow flame caused by the contamination of sodium, and expand the ability to see...
powdered for use for pigment purposes in ceramics and painting) was carried out at the Norwegian
BlaafarveværketBlaafarveværket in Modum, Norway, founded by King Christian VII of Denmark-Norway in the 1770s, became the largest industrial company of the country in the mid-19th century. The works mined cobalt ore and manufactured by smelting blue cobalt glass and cobalt blue pigment...
. The first mines for the production of
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
in the 16th to 18th century were located in Norway,
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
,
SaxonyThe Free State of Saxony is a landlocked state of Germany, contingent with Brandenburg, Saxony Anhalt, Thuringia, Bavaria, the Czech Republic and Poland. It is the tenth-largest German state in area, with of Germany's sixteen states....
and Hungary. With the discovery of cobalt ore in
New CaledoniaNew Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
in 1864 the mining of cobalt in Europe declined. With the discovery of ore deposits in
OntarioOntario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
,
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
in 1904 and the discovery of even larger deposits in the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
in the Congo in 1914 the mining operations shifted again. With the
Shaba conflictShaba II was an invasion of the Shaba separatist movement FNLC into the Zairian province of Shaba on 11 May 1978. The FNLC had its bases in eastern Angola and probably had the support of the Angolan government...
starting in the 1978 the main source for cobalt the copper mines of
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
nearly stopped their production. The impact on the world cobalt economy from this conflict was smaller than expected, because industry established effective ways for recycling cobalt materials and in some cases was able to change to cobalt-free alternatives.
In 1938, John Livingood and
Glenn T. SeaborgGlenn Theodore Seaborg was an American scientist who won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements", contributed to the discovery and isolation of ten elements, and developed the actinide concept, which led to the current arrangement of the...
discovered cobalt-60. This isotope was famously used at
Columbia UniversityColumbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
in the 1950s to establish
parityIn physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...
violation in radioactive
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
.
Occurrence
The stable form of cobalt is created in
supernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
s via the
r-processThe r-process is a nucleosynthesis process, likely occurring in core-collapse supernovae responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron. The process entails a succession of rapid neutron captures on seed nuclei, typically Ni-56,...
. It comprises
0.0029% of the Earth's crustThe abundance of a chemical element measures how relatively common the element is, or how much of the element is present in a given environment by comparison to all other elements...
and is one of the first
transition metalThe term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
series.
Cobalt occurs in copper and nickel minerals and in combination with
sulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and
arsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
in the sulfidic
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
(CoAsS),
saffloriteSafflorite is a rare cobalt iron arsenide mineral with formula: As2. Pure safflorite would be just CoAs2, but iron is virtually always present. Safflorite is a member of the three-way substitution series of arsenides known as the löllingite or löllingite group...
(CoAs
2) and
skutteruditeSkutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...
(CoAs
3) minerals. The mineral
cattieriteCattierite is a mineral found in the Democratic Republic of Congo. It was discovered together with Vaesite by Johannes F. Vaes, a Belgian mineralologist and named after Felicien Cattier, Chairman of the Board, Union Miniere du Haut Katanga....
is similar to
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
and occurs together with
vaesiteVaesite is a mineral found together with cattierite in the Democratic Republic of Congo. It is named after Johannes F. Vaes, a Belgian mineralologist.-References:**...
in the copper deposits of the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
. Upon contact with the atmosphere,
weatheringWeathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
occurs and the sulfide minerals oxidize to form pink
erythrite ("cobalt glance": Co
3(AsO
4)
2·8H
2O) and
sphaerocobaltiteSphaerocobaltite is a cobalt carbonate mineral with chemical composition CoCO3. In its pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown.-Further reading:*...
(CoCO
3).
Cobalt is not found as a
native metalA native metal is any metal that is found in its metallic form, either pure or as an alloy, in nature. Metals that can be found as native deposits singly and/or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, nickel, selenium, tantalum, tellurium,...
but is mainly obtained as a
by-productA by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....
of nickel and
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
mining activities. The main ores of cobalt are
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
,
erythrite,
glaucodotGlaucodot is a cobalt iron arsenic sulfide mineral with formula: AsS. The cobalt:iron ratio is typically 3:1 with minor nickel substituting. It forms a series with arsenopyrite . It is an opaque grey to tin-white typically found as massive forms without external crystal form. It crystallizes in the...
and
skutteruditeSkutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...
.
Production
In 2005, the copper deposits in the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
(former Shaba province) of the
Democratic Republic of the CongoThe Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
were the top producer of cobalt with almost 40% world share, reports the
British Geological SurveyThe British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
. The political situation in the Congo influences the price of cobalt significantly.
The Mukondo Mountain project, operated by the
Central African Mining and Exploration CompanyThe Central African Mining and Exploration Company was a mining company active in the Katanga Province of the Democratic Republic of the Congo and in other parts of Africa. It was acquired by ENRC in 2009.-Early years:...
in Katanga, may be the richest cobalt reserve in the world. It is estimated to be able to produce about one third of total global production of cobalt in 2008.
In July 2009 CAMEC announced a long term agreement under which CAMEC would deliver its entire annual production of cobalt in concentrate from Mukondo Mountain to Zhejiang Galico Cobalt & Nickel Materials of China.
Several methods exist for the separation of cobalt from copper and nickel. They depend on the concentration of cobalt and the exact composition of the used ore. One separation step involves
froth flotationFroth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries...
, in which surfactants bind to different ore components, leading to an enrichment of cobalt ores. Subsequent
roastingRoasting is a step in the processing of certain ores. More specifically, roasting is a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component. Often before roasting, the ore has already been partially purified, e.g. by froth...
converts the ores to the cobalt sulfate, whereas the copper and the iron are oxidized to the oxide. The
leachingLeaching is a widely used extractive metallurgy technique which converts metals into soluble salts in aqueous media. Compared to pyrometallurgical operations, leaching is easier to perform and much less harmful, because no gaseous pollution occurs...
with water extracts the sulfate together with the
arsenateThe arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....
s. The residues are further leached with
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
yielding a solution of copper sulfate. Cobalt can also be leached from the slag of the copper smelter.
The products of the above-mentioned processes are transformed into the cobalt oxide (Co
3O
4). This oxide is reduced to the metal by the
aluminothermic reactionAluminothermic reactions are exothermic chemical reactions using aluminium as the reducing agent at high temperature. The most prominent example is the thermite reaction between aluminium and iron oxides:-History:...
or reduction with carbon in a
blast furnaceA blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...
.
Alloys
Cobalt-based
superalloyA superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys typically have a matrix with an austenitic face-centered cubic crystal structure. ...
s consume most of the produced cobalt. The temperature stability of these alloys makes them suitable for use in turbine blades for gas
turbineA turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
s and jet
aircraftAn aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
engineAn engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
s, though nickel-based
single crystalA single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...
alloys surpass them in this regard. Cobalt-based alloys are also
corrosionCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
and wear-resistant. This makes them useful in the medical field, where cobalt is often used (along with
titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
) for orthopedic
implantAn implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, which is a transplanted biomedical tissue...
s that do not wear down over time. The development of the wear-resistant cobalt alloys started in the first decade of the 19th century with the
stelliteStellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon...
alloys, which are cobalt-chromium alloys with varying tungsten and carbon content. The formation of chromium and tungsten carbides makes them very hard and wear resistant. Special cobalt-
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
-
molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
alloys like
VitalliumVitallium is a trademark for an alloy of 60% cobalt, 20% chromium, 5% molybdenum, and other substances. The alloy is used in dentistry and artificial joints, because of its light weight and resistance to corrosion. It is also used for components of turbochargers because of its thermal resistance....
are used for prosthetic parts such as hip and knee replacements. Cobalt alloys are also used for dental prosthetics, where they are useful to avoid allergies to nickel. Some
high speed steelHigh speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
s also use cobalt to increase heat and wear-resistance. The special alloys of aluminium, nickel, cobalt and iron, known as
AlnicoAlnico is an acronym referring to iron alloys which in addition to iron are composed primarily of aluminium , nickel and cobalt , hence al-ni-co, with the addition of copper, and sometimes titanium. Alnico alloys are ferromagnetic, with a high coercivity and are used to make permanent magnets...
, and of samarium and cobalt (
samarium-cobalt magnetA samarium–cobalt magnet, a type of rare earth magnet, is a strong permanent magnet made of an alloy of samarium and cobalt. They were developed in the early 1970s. They are generally the second-strongest type of magnet made, less strong than neodymium magnets, but have higher temperature ratings...
) are used in permanent magnets.
It is also alloyed with 95%
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
for jewelry purposes, yielding an alloy that is suitable for fine detailed casting and is also slightly magnetic.
Batteries
Lithium cobalt oxideLithium cobalt oxide is a chemical compound commonly used in the positive electrodes of lithium-ion batteries. The structure of LiCoO2 is known theoretically and has been confirmed with techniques like x-ray diffraction, electron microscopy, neutron powder diffraction, and EXAFS: it consists of...
(LiCoO
2) is widely used in
lithium ion batteryA lithium-ion battery is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types...
cathodes. The material is composed of cobalt oxide layers in which the lithium is
intercalatedIn chemistry, intercalation is the reversible inclusion of a molecule between two other molecules . Examples include DNA intercalation and graphite intercalation compounds.- DNA intercalation :...
. During discharging the lithium intercalated between the layers is set free as lithium ion.
Nickel-cadmiumThe nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
(NiCd) and
nickel metal hydrideA nickel–metal hydride cell, abbreviated NiMH, is a type of rechargeable battery similar to the nickel–cadmium cell. The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd cells, the positive electrode is nickel oxyhydroxide...
(NiMH) batteries also contain significant amounts of cobalt; the cobalt improves the oxidation capabilities of nickel in the battery.
Catalysis
Several cobalt compounds are used in chemical reactions as oxidation catalysts. Cobalt acetate is used for the conversion of
xyleneXylene encompasses three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- , meta- , and para- , which specify to which carbon atoms the two methyl groups are attached...
to
terephthalic acidTerephthalic acid is the organic compound with formula C6H42. This colourless solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several billion kilograms are produced annually...
, the precursor to the bulk polymer
polyethylene terephthalatePolyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
. Typical catalysts are the cobalt carboxylates (known as cobalt soaps). They are also used in paints, varnishes, and inks as "drying agents" through the oxidation of drying oils. The same carboxylates are used to improve the adhesion of the steel to rubber in steel-belted radial tires.
Cobalt-based catalysts are also important in reactions involving
carbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
.
Steam reformingFossil fuel reforming is a method of producing hydrogen or other useful products from fossil fuels such as natural gas. This is achieved in a processing device called a reformer which reacts steam at high temperature with the fossil fuel. The steam methane reformer is widely used in industry to...
, useful in
hydrogen productionHydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...
, uses cobalt oxide-base catalysts. Cobalt is also a catalyst in the
Fischer-Tropsch processThe Fischer–Tropsch process is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic...
, used in the
hydrogenationHydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
of carbon monoxide into liquid fuels. The
hydroformylationHydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
of
alkeneIn organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s often rely on cobalt octacarbonyl as the catalyst, although such processes have been partially displaced by more efficient iridium- and rhodium-based catalysts, e.g. the
Cativa processThe Cativa process is a method for the production of acetic acid by the carbonylation of methanol. The technology, which is similar to the Monsanto process, was developed by BP Chemicals and is under license by BP Plc...
.
The
hydrodesulfurizationHydrodesulfurization is a catalytic chemical process widely used to remove sulfur from natural gas and from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils...
of
petroleumPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
uses a catalyst derived from cobalt and molybdenum. This process helps to rid petroleum of sulfur impurities that interfere with the refining of liquid fuels.
Pigments and coloring
Before the 19th century, the predominant use of cobalt was as pigment. Since the Middle Ages, it has been involved in the production of
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
, a blue colored glass. Smalt is produced by melting a mixture of the roasted mineral
smaltiteSmaltite is a variety of the mineral skutterudite consisting of cobalt iron nickel arsenide: As2.Smaltite crystallizes in the cubic system with the same hemihedral symmetry as pyrite; crystals have usually the form of cubes or cubo-octahedra, but are imperfectly developed and of somewhat rare...
,
quartzQuartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and
potassium carbonatePotassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
, yielding a dark blue silicate glass which is ground after the production. Smalt was widely used for the coloration of glass and as pigment for paintings. In 1780,
Sven RinmanSven Rinman was a Swedish chemist and mineralogist who discovered the pigment cobalt green, sometimes also called Rinman's green. He had a great influence on mining and the steel production in Sweden.-Life and work:...
discovered
cobalt greenCobalt green, sometimes known as Rinman's green or Zinc Green, is a translucent green pigment made by heating a mixture of cobalt oxide and zinc oxide. Sven Rinman, a Swedish chemist, discovered this compound in 1780. Although it is stable and can be safely mixed with other pigments, it is rarely...
and in 1802
Louis Jacques ThénardLouis Jacques Thénard , was a French chemist.His father, a poor peasant, managed to have him educated at the academy of Sens, and sent him at the age of sixteen to study pharmacy in Paris. There he attended the lectures of Antoine François Fourcroy and Louis Nicolas Vauquelin...
discovered
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
. The two varieties of cobalt blue, cobalt aluminate and cobalt green (a mixture of
cobalt(II) oxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
and
zinc oxideZinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...
), were used as pigments for paintings because of their superior stability.
Radioisotopes
Cobalt-60 (Co-60 or
60Co) is useful as a gamma ray source because it can be produced in predictable quantity and high activity by bombarding cobalt with
neutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s. It produces two
gamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s with energies of 1.17 and 1.33
MeVMeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...
.
Its uses include
external beam radiotherapyExternal beam radiotherapy or teletherapy is the most common form of radiotherapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body...
, sterilization of medical supplies and medical waste, radiation treatment of
foods for sterilizationFood irradiation is the process of exposing food to ionizing radiation to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration...
(cold
pasteurizationPasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
), industrial
radiographyRadiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
(e.g. weld integrity radiographs), density measurements (e.g. concrete density measurements), and tank fill height switches. The metal has the unfortunate habit of producing a fine dust, causing problems with radiation protection. Cobalt from radiotherapy machines has been a serious hazard when not disposed of properly, and one of the worst radiation contamination accidents in North America occurred in 1984, after a discarded radiotherapy unit containing cobalt-60 was mistakenly disassembled in a junkyard in Juarez, Mexico.
Cobalt-60 has a radioactive half-life of 5.27 years. This decrease in activity requires periodic replacement of the sources used in radiotherapy and is one reason why cobalt machines have been largely replaced by
linear acceleratorA linear particle accelerator is a type of particle accelerator that greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline; this method of particle acceleration was invented...
s in modern radiation therapy.
Cobalt-57 (Co-57 or
57Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for
vitamin B
{{about|the metal}}
Cobalt (icon or ˈ) is a chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with symbol
Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray
metalA metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
.
Cobalt-based blue pigments have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was later thought by alchemists to be due to the known metal
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
. Miners had long used the name
koboldThe kobold is a sprite stemming from Germanic mythology and surviving into modern times in German folklore. Although usually invisible, a kobold can materialise in the form of an animal, fire, a human being, and a candle. The most common depictions of kobolds show them as humanlike figures the size...
ore (German for
goblin ore) for some of the blue-pigment producing minerals; they were named because they were poor in known metals and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the
kobold.
Nowadays, some cobalt is produced specifically from various metallic-lustered ores, for example
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
(CoAsS), but the main source of the element is as a by-product of
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
and
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
mining. The copper belt in the
Democratic Republic of the CongoThe Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
and
ZambiaZambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
yields most of the cobalt metal mined worldwide.
Cobalt is used in the preparation of
magneticMagnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
, wear-resistant and high-strength
alloyAn alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s. Cobalt silicate and cobalt(II) aluminate (CoAl
2O
4,
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
) give a distinctive deep blue color to
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
,
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
, ceramics,
inkInk is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...
s,
paintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
s and
varnishVarnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
es. Cobalt occurs naturally as only one stable isotope, cobalt-59.
Cobalt-60Cobalt-60, , is a synthetic radioactive isotope of cobalt. Due to its half-life of 5.27 years, is not found in nature. It is produced artificially by neutron activation of . decays by beta decay to the stable isotope nickel-60...
is a commercially important radioisotope, used as a
radioactive tracerA radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...
and in the production of
gamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s.
Cobalt is the active center of coenzymes called cobalamins, the most common example of which is
vitamin B12Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
. As such it is an essential trace
dietary mineralDietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
for all animals. Cobalt in inorganic form is also an active nutrient for bacteria,
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and fungi.
Characteristics
Cobalt is a
ferromagneticFerromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished...
metal with a
specific gravitySpecific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 8.9. Pure cobalt is not found in nature, but compounds of cobalt are common. Small amounts of it are found in most rocks, soil, plants and animals. The Curie temperature is 1115 °C and the magnetic moment is 1.6–1.7
Bohr magnetons per
atomThe atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
. In nature, it is frequently associated with nickel, and both are characteristic minor components of meteoric iron. Cobalt has a
relative permeabilityIn electromagnetism, permeability is the measure of the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field. Magnetic permeability is typically...
two thirds that of
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. Metallic cobalt occurs as two crystallographic structures: hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the energy difference is so small that random intergrowth of the two is common.
Cobalt is a weakly reducing metal that is protected from oxidation by a
passivatingPassivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...
oxide film. It is attacked by halogens and sulfur. Heating in oxygen produces
Co3O4Cobalt oxide is inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid...
which loses oxygen at 900 °C to give the
monoxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
CoO.
Compounds
{{Category see also|Cobalt compounds}}
Common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +4 are also known. A common oxidation state for simple compounds is +2. Cobalt(II) salts form the red-pink [Co(H
2O)
6]
2+ complex in aqueous solution. Addition of chloride gives the intensely blue .
Oxygen and chalcogen compounds
Several
oxideAn oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s of cobalt are known. Green
cobalt(II) oxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
(CoO) has
rocksaltIn crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....
structure. It is readily oxidized with water and oxygen to brown cobalt(III) hydroxide (Co(OH)
3). At temperatures of 600–700 °C, CoO oxidizes to the blue
cobalt(II,III) oxideCobalt oxide is inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid...
(Co
3O
4), which has a
spinelSpinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
structure. Black
cobalt(III) oxideCobalt oxide is the inorganic compound with the formula Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co salts such as cobalt nitrate with an aqueous solution of sodium hypochlorite gives a...
(Co
2O
3) is also known. Cobalt oxides are antiferromagnetic at low
temperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
: CoO (
Neel temperatureThe Néel temperature or magnetic ordering temperature , TN, is the temperature above which an antiferromagnetic material becomes paramagnetic—that is, the thermal energy becomes large enough to destroy the macroscopic magnetic ordering within the material....
291 K) and Co
3O
4 (Neel temperature: 40 K), which is analogous to
magnetiteMagnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
(Fe
3O
4), with a mixture of +2 and +3 oxidation states.
The principal
chalcogenThe chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...
ides of cobalt include the black cobalt(II) sulfides, CoS
2, which adopts a
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
-like structure, and Co
2S
3.
PentlanditePentlandite is an iron-nickel sulfide, 9S8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt.Pentlandite forms isometric crystals, but is normally found in massive granular aggregates. It is brittle with a hardness of 3.5 - 4 and specific gravity of 4.6 - 5.0 and...
(Co
9S
8) is metal-rich.
Halides
The four dihalides of cobalt(II) are known:
cobalt(II) fluorideCobalt fluoride is a chemical compound with the formula . It is a pink crystalline solid compound. The formula is given for both the red tetragonal crystal, , and the tetrahydrate red orthogonal crystal, . CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it...
(CoF
2, pink),
cobalt(II) chlorideCobalt chloride is an inorganic compound of cobalt and chloride, with the formula CoCl2. It is usually supplied as the hexahydrate CoCl2·6H2O, which is one of the most commonly used cobalt compounds in the laboratory. The hexahydrate is deep purple in color, whereas the anhydrous form is sky blue...
(CoCl
2, blue),
cobalt(II) bromideCobalt bromide is an inorganic compound used primarily as a catalyst in some processes.-Properties:When anhydrous, cobalt bromide appears as green crystals. The hexahydrate loses four waters of crystallization molecules at 100°C forming the dihydrate:Further heating to 130°C Produces the anhydrous...
(CoBr
2, green),
cobalt(II) iodideCobalt iodide or cobaltous iodide is the inorganic compound composed with the formula Co I2. The two forms of CoI2 and the hydrated form are the principal iodides of cobalt.-Synthesis and structure:...
(CoI
2, blue-black). These halides exist as anhydrous and hydrates. Whereas the anhydrous dichloride is blue, the hydrate is red.
The reduction potential for the reaction
- + →
is +1.92 V, beyond that for
chlorineChlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
to chloride, +1.36 V. As a consequence cobalt(III) and chloride would result in the cobalt(III) being reduced to cobalt(II). Because the reduction potential for fluorine to fluoride is so high, +2.87 V, cobalt(III) fluoride is one of the few simple stable cobalt(III) compounds. Cobalt(III) fluoride, which is used in some fluorination reactions, reacts vigorously with water.
Coordination compounds
As for all metals, molecular compounds of cobalt are classified as coordination complexes, that is molecules or ions that contain cobalt linked to several
ligandIn coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s. The principles of
electronegativityElectronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
and
hardness–softnessThe HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
of a series of ligands can be used to explain the usual oxidation state of the cobalt. For example Co
+3 complexes tend to have
ammineIn coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelled with a single "m"...
ligands. As phosphorus is softer than nitrogen, phosphine ligands tend to feature the
softerThe HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
Co
2+ and Co
+, an example being tris(triphenylphosphine)cobalt(I) chloride ((P(C
6H
5)
3)
3CoCl). The more electronegative (and harder) oxide and fluoride can stabilize Co
4+ derivatives, e.g. caesium hexafluorocobaltate (Cs
2CoF
6) and potassium percobaltate (K
3CoO
4).
Alfred WernerAlfred Werner was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry...
, a Nobel-prize winning pioneer in coordination chemistry, worked with compounds of
empirical formulaIn chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic...
CoCl
3(NH
3)
6. One of the isomers determined was
cobalt(III) hexammine chlorideHexamminecobalt chloride is the chemical compound with the formula [Co6]Cl3. This coordination compound is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner. This salt consists of [Co6]3+ trications with three Cl− anions...
. This coordination complex, a "typical" Werner-type complex, consists of a central cobalt atom coordinated by six
ammineIn coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelled with a single "m"...
ligands orthogonal to each other and three
chlorideThe chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
counteranions. Using chelating ethylenediamine ligands in place of ammonia gives
tris(ethylenediamine)cobalt(III) chlorideTriscobalt chloride is a coordination complex with the formula [Co3]Cl3 . This complex was important in the history of coordination chemistry because of its stability and its stereochemistry. Many different salts have been described...
([Co(en)
3]Cl), which was one of the first coordination complexes that was resolved into
optical isomersA chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
. The complex exists as both either right- or left-handed forms of a "three-bladed propeller". This complex was first isolated by Werner as yellow-gold needle-like crystals.
Organometallic compounds
{{Main|Organocobalt chemistry}}
CobaltoceneCobaltocene, known also as biscobalt or even "bis Cp cobalt", is an organocobalt compound with the formula Co2. It is a dark purple solid that sublimes readily slightly above room temperature. Cobaltocene was discovered shortly after ferrocene, the first metallocene...
is a structural analog to
ferroceneFerrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds...
, where cobalt substitutes for iron. Cobaltocene is sensitive to oxidation, much more than ferrocene. Cobalt carbonyl (Co
2(CO)
8) is a
catalystCatalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
in
carbonylationCarbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry.-Organic chemistry:...
reactions.
Vitamin B12Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
(see below) is an organometallic compound found in nature and is the only
vitaminA vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
to contain a metal atom.
Isotopes
{{Main|Isotopes of cobalt}}
59Co is the only stable cobalt
isotopeIsotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
and the only isotope to exist in nature. 22 radioisotopes have been characterized with the most stable being
60Co with a
half-lifeHalf-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 5.2714 years,
57Co with a half-life of 271.79 days,
56Co with a half-life of 77.27 days, and
58Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are shorter than 18 hours, and the majority of these are shorter than 1 second. This element also has 4 meta states, all of which have half-lives shorter than 15 minutes.
The isotopes of cobalt range in
atomic weightAtomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
from 50
uThe unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
(
50Co) to 73 u (
73Co). The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope,
59Co, is
electron captureElectron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
and the primary mode of decay for those of greater than 59 atomic mass units is
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
. The primary
decay productIn nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...
s before
59Co are element 26 (
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
) isotopes and the primary products after are element 28 (nickel) isotopes.
History
Cobalt compounds have been used for centuries to impart a rich blue color to
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
,
glazesGlaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
and
ceramicsIn art history, ceramics and ceramic art mean art objects such as figures, tiles, and tableware made from clay and other raw materials by the process of pottery. Some ceramic products are regarded as fine art, while others are regarded as decorative, industrial or applied art objects, or as...
. Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of
PompeiiThe city of Pompeii is a partially buried Roman town-city near modern Naples in the Italian region of Campania, in the territory of the comune of Pompei. Along with Herculaneum, Pompeii was destroyed and completely buried during a long catastrophic eruption of the volcano Mount Vesuvius spanning...
(destroyed in 79 AD), and in China dating from the
Tang dynastyThe Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
(618–907 AD) and the
Ming dynastyThe Ming Dynasty, also Empire of the Great Ming, was the ruling dynasty of China from 1368 to 1644, following the collapse of the Mongol-led Yuan Dynasty. The Ming, "one of the greatest eras of orderly government and social stability in human history", was the last dynasty in China ruled by ethnic...
(1368–1644 AD).
Cobalt has been used to color glass since the
Bronze AgeThe Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...
. The excavation of the
Uluburun shipwreckThe Uluburun Shipwreck is a Late Bronze Age shipwreck dated to the late 14th century BCE, discovered off Uluburun situated about 6 miles southeast of Kaş, in south-western Turkey...
yielded an ingot of blue glass, which was cast during the 14th century BC. Blue glass items from Egypt are colored with copper, iron, or cobalt. The oldest cobalt-colored glass was from the time of the
Eighteenth dynastyThe eighteenth dynasty of ancient Egypt is perhaps the best known of all the dynasties of ancient Egypt...
in
EgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
(1550–1292 BC). The location where the cobalt compounds were obtained is unknown.
The word
cobalt is derived from the German
{{lang|mhd|kobalt}}, from
koboldThe kobold is a sprite stemming from Germanic mythology and surviving into modern times in German folklore. Although usually invisible, a kobold can materialise in the form of an animal, fire, a human being, and a candle. The most common depictions of kobolds show them as humanlike figures the size...
meaning "goblin", a superstitious term used for the
oreAn ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
of cobalt by miners. The first attempts at smelting these ores to produce metals such as copper or nickel failed, yielding simply powder (cobalt(II) oxide) instead. Also, because the primary ores of cobalt always contain
arsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, smelting the ore oxidized the arsenic content into the highly toxic and volatile arsenic oxide, which also decreased the reputation of the ore for the miners.
Swedish chemist
Georg Brandt-External links:** by Uno Boklund in: Charles C. Gillispie, ed., Dictionary of Scientific Biography , vol. 2, pages 421-422....
(1694–1768) is credited with discovering cobalt circa 1735, showing it to be a new previously unknown element different from bismuth and other traditional metals, and calling it a new "semi-metal." He was able to show that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period, during which all the known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers.
During the 19th century, a significant part of the world's production of
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
(a dye made with cobalt compounds and alumina) and
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
(
cobalt glassCobalt glass is a deep blue colored glass prepared by adding cobalt compounds to the molten glass. It is appreciated for its attractive color. It is also used as an optical filter in flame tests to filter out the yellow flame caused by the contamination of sodium, and expand the ability to see...
powdered for use for pigment purposes in ceramics and painting) was carried out at the Norwegian
BlaafarveværketBlaafarveværket in Modum, Norway, founded by King Christian VII of Denmark-Norway in the 1770s, became the largest industrial company of the country in the mid-19th century. The works mined cobalt ore and manufactured by smelting blue cobalt glass and cobalt blue pigment...
. The first mines for the production of
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
in the 16th to 18th century were located in Norway,
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
,
SaxonyThe Free State of Saxony is a landlocked state of Germany, contingent with Brandenburg, Saxony Anhalt, Thuringia, Bavaria, the Czech Republic and Poland. It is the tenth-largest German state in area, with of Germany's sixteen states....
and Hungary. With the discovery of cobalt ore in
New CaledoniaNew Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
in 1864 the mining of cobalt in Europe declined. With the discovery of ore deposits in
OntarioOntario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
,
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
in 1904 and the discovery of even larger deposits in the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
in the Congo in 1914 the mining operations shifted again. With the
Shaba conflictShaba II was an invasion of the Shaba separatist movement FNLC into the Zairian province of Shaba on 11 May 1978. The FNLC had its bases in eastern Angola and probably had the support of the Angolan government...
starting in the 1978 the main source for cobalt the copper mines of
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
nearly stopped their production. The impact on the world cobalt economy from this conflict was smaller than expected, because industry established effective ways for recycling cobalt materials and in some cases was able to change to cobalt-free alternatives.
In 1938, John Livingood and
Glenn T. SeaborgGlenn Theodore Seaborg was an American scientist who won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements", contributed to the discovery and isolation of ten elements, and developed the actinide concept, which led to the current arrangement of the...
discovered cobalt-60. This isotope was famously used at
Columbia UniversityColumbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
in the 1950s to establish
parityIn physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...
violation in radioactive
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
.
Occurrence
The stable form of cobalt is created in
supernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
s via the
r-processThe r-process is a nucleosynthesis process, likely occurring in core-collapse supernovae responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron. The process entails a succession of rapid neutron captures on seed nuclei, typically Ni-56,...
. It comprises
0.0029% of the Earth's crustThe abundance of a chemical element measures how relatively common the element is, or how much of the element is present in a given environment by comparison to all other elements...
and is one of the first
transition metalThe term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
series.
Cobalt occurs in copper and nickel minerals and in combination with
sulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and
arsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
in the sulfidic
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
(CoAsS),
saffloriteSafflorite is a rare cobalt iron arsenide mineral with formula: As2. Pure safflorite would be just CoAs2, but iron is virtually always present. Safflorite is a member of the three-way substitution series of arsenides known as the löllingite or löllingite group...
(CoAs
2) and
skutteruditeSkutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...
(CoAs
3) minerals. The mineral
cattieriteCattierite is a mineral found in the Democratic Republic of Congo. It was discovered together with Vaesite by Johannes F. Vaes, a Belgian mineralologist and named after Felicien Cattier, Chairman of the Board, Union Miniere du Haut Katanga....
is similar to
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
and occurs together with
vaesiteVaesite is a mineral found together with cattierite in the Democratic Republic of Congo. It is named after Johannes F. Vaes, a Belgian mineralologist.-References:**...
in the copper deposits of the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
. Upon contact with the atmosphere,
weatheringWeathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
occurs and the sulfide minerals oxidize to form pink
erythrite ("cobalt glance": Co
3(AsO
4)
2·8H
2O) and
sphaerocobaltiteSphaerocobaltite is a cobalt carbonate mineral with chemical composition CoCO3. In its pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown.-Further reading:*...
(CoCO
3).
Cobalt is not found as a
native metalA native metal is any metal that is found in its metallic form, either pure or as an alloy, in nature. Metals that can be found as native deposits singly and/or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, nickel, selenium, tantalum, tellurium,...
but is mainly obtained as a
by-productA by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....
of nickel and
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
mining activities. The main ores of cobalt are
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
,
erythrite,
glaucodotGlaucodot is a cobalt iron arsenic sulfide mineral with formula: AsS. The cobalt:iron ratio is typically 3:1 with minor nickel substituting. It forms a series with arsenopyrite . It is an opaque grey to tin-white typically found as massive forms without external crystal form. It crystallizes in the...
and
skutteruditeSkutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...
.
Production
{{See also|Cobalt extraction techniques}}
In 2005, the copper deposits in the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
(former Shaba province) of the
Democratic Republic of the CongoThe Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
were the top producer of cobalt with almost 40% world share, reports the
British Geological SurveyThe British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
. The political situation in the Congo influences the price of cobalt significantly.
The Mukondo Mountain project, operated by the
Central African Mining and Exploration CompanyThe Central African Mining and Exploration Company was a mining company active in the Katanga Province of the Democratic Republic of the Congo and in other parts of Africa. It was acquired by ENRC in 2009.-Early years:...
in Katanga, may be the richest cobalt reserve in the world. It is estimated to be able to produce about one third of total global production of cobalt in 2008.
In July 2009 CAMEC announced a long term agreement under which CAMEC would deliver its entire annual production of cobalt in concentrate from Mukondo Mountain to Zhejiang Galico Cobalt & Nickel Materials of China.
Several methods exist for the separation of cobalt from copper and nickel. They depend on the concentration of cobalt and the exact composition of the used ore. One separation step involves
froth flotationFroth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries...
, in which surfactants bind to different ore components, leading to an enrichment of cobalt ores. Subsequent
roastingRoasting is a step in the processing of certain ores. More specifically, roasting is a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component. Often before roasting, the ore has already been partially purified, e.g. by froth...
converts the ores to the cobalt sulfate, whereas the copper and the iron are oxidized to the oxide. The
leachingLeaching is a widely used extractive metallurgy technique which converts metals into soluble salts in aqueous media. Compared to pyrometallurgical operations, leaching is easier to perform and much less harmful, because no gaseous pollution occurs...
with water extracts the sulfate together with the
arsenateThe arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....
s. The residues are further leached with
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
yielding a solution of copper sulfate. Cobalt can also be leached from the slag of the copper smelter.
The products of the above-mentioned processes are transformed into the cobalt oxide (Co
3O
4). This oxide is reduced to the metal by the
aluminothermic reactionAluminothermic reactions are exothermic chemical reactions using aluminium as the reducing agent at high temperature. The most prominent example is the thermite reaction between aluminium and iron oxides:-History:...
or reduction with carbon in a
blast furnaceA blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...
.
Alloys
Cobalt-based
superalloyA superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys typically have a matrix with an austenitic face-centered cubic crystal structure. ...
s consume most of the produced cobalt. The temperature stability of these alloys makes them suitable for use in turbine blades for gas
turbineA turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
s and jet
aircraftAn aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
engineAn engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
s, though nickel-based
single crystalA single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...
alloys surpass them in this regard. Cobalt-based alloys are also
corrosionCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
and wear-resistant. This makes them useful in the medical field, where cobalt is often used (along with
titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
) for orthopedic
implantAn implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, which is a transplanted biomedical tissue...
s that do not wear down over time. The development of the wear-resistant cobalt alloys started in the first decade of the 19th century with the
stelliteStellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon...
alloys, which are cobalt-chromium alloys with varying tungsten and carbon content. The formation of chromium and tungsten carbides makes them very hard and wear resistant. Special cobalt-
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
-
molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
alloys like
VitalliumVitallium is a trademark for an alloy of 60% cobalt, 20% chromium, 5% molybdenum, and other substances. The alloy is used in dentistry and artificial joints, because of its light weight and resistance to corrosion. It is also used for components of turbochargers because of its thermal resistance....
are used for prosthetic parts such as hip and knee replacements. Cobalt alloys are also used for dental prosthetics, where they are useful to avoid allergies to nickel. Some
high speed steelHigh speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
s also use cobalt to increase heat and wear-resistance. The special alloys of aluminium, nickel, cobalt and iron, known as
AlnicoAlnico is an acronym referring to iron alloys which in addition to iron are composed primarily of aluminium , nickel and cobalt , hence al-ni-co, with the addition of copper, and sometimes titanium. Alnico alloys are ferromagnetic, with a high coercivity and are used to make permanent magnets...
, and of samarium and cobalt (
samarium-cobalt magnetA samarium–cobalt magnet, a type of rare earth magnet, is a strong permanent magnet made of an alloy of samarium and cobalt. They were developed in the early 1970s. They are generally the second-strongest type of magnet made, less strong than neodymium magnets, but have higher temperature ratings...
) are used in permanent magnets.
[{{cite journal|title = Reproducing the Properties of Alnico Permanent Magnet Alloys with Elongated Single-Domain Cobalt-Iron Particles|journal = Journal Applied Physics|volume = 28|issue = 344|year = 1957|doi = 10.1063/1.1722744|first = F. E.|last = Luborsky|coauthors = Mendelsohn, L. I.; Paine, T. O.|page = 344|bibcode = 1957JAP....28..344L }}] It is also alloyed with 95%
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
for jewelry purposes, yielding an alloy that is suitable for fine detailed casting and is also slightly magnetic.
Batteries
Lithium cobalt oxideLithium cobalt oxide is a chemical compound commonly used in the positive electrodes of lithium-ion batteries. The structure of LiCoO2 is known theoretically and has been confirmed with techniques like x-ray diffraction, electron microscopy, neutron powder diffraction, and EXAFS: it consists of...
(LiCoO
2) is widely used in
lithium ion batteryA lithium-ion battery is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types...
cathodes. The material is composed of cobalt oxide layers in which the lithium is
intercalatedIn chemistry, intercalation is the reversible inclusion of a molecule between two other molecules . Examples include DNA intercalation and graphite intercalation compounds.- DNA intercalation :...
. During discharging the lithium intercalated between the layers is set free as lithium ion.
Nickel-cadmiumThe nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
(NiCd) and
nickel metal hydrideA nickel–metal hydride cell, abbreviated NiMH, is a type of rechargeable battery similar to the nickel–cadmium cell. The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd cells, the positive electrode is nickel oxyhydroxide...
(NiMH) batteries also contain significant amounts of cobalt; the cobalt improves the oxidation capabilities of nickel in the battery.
Catalysis
Several cobalt compounds are used in chemical reactions as oxidation catalysts. Cobalt acetate is used for the conversion of
xyleneXylene encompasses three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- , meta- , and para- , which specify to which carbon atoms the two methyl groups are attached...
to
terephthalic acidTerephthalic acid is the organic compound with formula C6H42. This colourless solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several billion kilograms are produced annually...
, the precursor to the bulk polymer
polyethylene terephthalatePolyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
. Typical catalysts are the cobalt carboxylates (known as cobalt soaps). They are also used in paints, varnishes, and inks as "drying agents" through the oxidation of drying oils. The same carboxylates are used to improve the adhesion of the steel to rubber in steel-belted radial tires.
Cobalt-based catalysts are also important in reactions involving
carbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
.
Steam reformingFossil fuel reforming is a method of producing hydrogen or other useful products from fossil fuels such as natural gas. This is achieved in a processing device called a reformer which reacts steam at high temperature with the fossil fuel. The steam methane reformer is widely used in industry to...
, useful in
hydrogen productionHydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...
, uses cobalt oxide-base catalysts. Cobalt is also a catalyst in the
Fischer-Tropsch processThe Fischer–Tropsch process is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic...
, used in the
hydrogenationHydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
of carbon monoxide into liquid fuels. The
hydroformylationHydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
of
alkeneIn organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s often rely on cobalt octacarbonyl as the catalyst, although such processes have been partially displaced by more efficient iridium- and rhodium-based catalysts, e.g. the
Cativa processThe Cativa process is a method for the production of acetic acid by the carbonylation of methanol. The technology, which is similar to the Monsanto process, was developed by BP Chemicals and is under license by BP Plc...
.
The
hydrodesulfurizationHydrodesulfurization is a catalytic chemical process widely used to remove sulfur from natural gas and from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils...
of
petroleumPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
uses a catalyst derived from cobalt and molybdenum. This process helps to rid petroleum of sulfur impurities that interfere with the refining of liquid fuels.
Pigments and coloring
Before the 19th century, the predominant use of cobalt was as pigment. Since the Middle Ages, it has been involved in the production of
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
, a blue colored glass. Smalt is produced by melting a mixture of the roasted mineral
smaltiteSmaltite is a variety of the mineral skutterudite consisting of cobalt iron nickel arsenide: As2.Smaltite crystallizes in the cubic system with the same hemihedral symmetry as pyrite; crystals have usually the form of cubes or cubo-octahedra, but are imperfectly developed and of somewhat rare...
,
quartzQuartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and
potassium carbonatePotassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
, yielding a dark blue silicate glass which is ground after the production. Smalt was widely used for the coloration of glass and as pigment for paintings. In 1780,
Sven RinmanSven Rinman was a Swedish chemist and mineralogist who discovered the pigment cobalt green, sometimes also called Rinman's green. He had a great influence on mining and the steel production in Sweden.-Life and work:...
discovered
cobalt greenCobalt green, sometimes known as Rinman's green or Zinc Green, is a translucent green pigment made by heating a mixture of cobalt oxide and zinc oxide. Sven Rinman, a Swedish chemist, discovered this compound in 1780. Although it is stable and can be safely mixed with other pigments, it is rarely...
and in 1802
Louis Jacques ThénardLouis Jacques Thénard , was a French chemist.His father, a poor peasant, managed to have him educated at the academy of Sens, and sent him at the age of sixteen to study pharmacy in Paris. There he attended the lectures of Antoine François Fourcroy and Louis Nicolas Vauquelin...
discovered
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
. The two varieties of cobalt blue, cobalt aluminate and cobalt green (a mixture of
cobalt(II) oxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
and
zinc oxideZinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...
), were used as pigments for paintings because of their superior stability.
Radioisotopes
Cobalt-60 (Co-60 or
60Co) is useful as a gamma ray source because it can be produced in predictable quantity and high activity by bombarding cobalt with
neutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s. It produces two
gamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s with energies of 1.17 and 1.33
MeVMeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...
.
Its uses include
external beam radiotherapyExternal beam radiotherapy or teletherapy is the most common form of radiotherapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body...
, sterilization of medical supplies and medical waste, radiation treatment of
foods for sterilizationFood irradiation is the process of exposing food to ionizing radiation to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration...
(cold
pasteurizationPasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
), industrial
radiographyRadiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
(e.g. weld integrity radiographs), density measurements (e.g. concrete density measurements), and tank fill height switches. The metal has the unfortunate habit of producing a fine dust, causing problems with radiation protection. Cobalt from radiotherapy machines has been a serious hazard when not disposed of properly, and one of the worst radiation contamination accidents in North America occurred in 1984, after a discarded radiotherapy unit containing cobalt-60 was mistakenly disassembled in a junkyard in Juarez, Mexico.
Cobalt-60 has a radioactive half-life of 5.27 years. This decrease in activity requires periodic replacement of the sources used in radiotherapy and is one reason why cobalt machines have been largely replaced by
linear acceleratorA linear particle accelerator is a type of particle accelerator that greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline; this method of particle acceleration was invented...
s in modern radiation therapy.
Cobalt-57 (Co-57 or
57Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for
vitamin B
{{about|the metal}}
Cobalt (icon or ˈ) is a chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with symbol
Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray
metalA metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
.
Cobalt-based blue pigments have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was later thought by alchemists to be due to the known metal
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
. Miners had long used the name
koboldThe kobold is a sprite stemming from Germanic mythology and surviving into modern times in German folklore. Although usually invisible, a kobold can materialise in the form of an animal, fire, a human being, and a candle. The most common depictions of kobolds show them as humanlike figures the size...
ore (German for
goblin ore) for some of the blue-pigment producing minerals; they were named because they were poor in known metals and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the
kobold.
Nowadays, some cobalt is produced specifically from various metallic-lustered ores, for example
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
(CoAsS), but the main source of the element is as a by-product of
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
and
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
mining. The copper belt in the
Democratic Republic of the CongoThe Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
and
ZambiaZambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
yields most of the cobalt metal mined worldwide.
Cobalt is used in the preparation of
magneticMagnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
, wear-resistant and high-strength
alloyAn alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s. Cobalt silicate and cobalt(II) aluminate (CoAl
2O
4,
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
) give a distinctive deep blue color to
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
,
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
, ceramics,
inkInk is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...
s,
paintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
s and
varnishVarnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
es. Cobalt occurs naturally as only one stable isotope, cobalt-59.
Cobalt-60Cobalt-60, , is a synthetic radioactive isotope of cobalt. Due to its half-life of 5.27 years, is not found in nature. It is produced artificially by neutron activation of . decays by beta decay to the stable isotope nickel-60...
is a commercially important radioisotope, used as a
radioactive tracerA radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...
and in the production of
gamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s.
Cobalt is the active center of coenzymes called cobalamins, the most common example of which is
vitamin B12Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
. As such it is an essential trace
dietary mineralDietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
for all animals. Cobalt in inorganic form is also an active nutrient for bacteria,
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and fungi.
Characteristics
Cobalt is a
ferromagneticFerromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished...
metal with a
specific gravitySpecific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 8.9. Pure cobalt is not found in nature, but compounds of cobalt are common. Small amounts of it are found in most rocks, soil, plants and animals. The Curie temperature is 1115 °C and the magnetic moment is 1.6–1.7
Bohr magnetons per
atomThe atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
. In nature, it is frequently associated with nickel, and both are characteristic minor components of meteoric iron. Cobalt has a
relative permeabilityIn electromagnetism, permeability is the measure of the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field. Magnetic permeability is typically...
two thirds that of
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. Metallic cobalt occurs as two crystallographic structures: hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the energy difference is so small that random intergrowth of the two is common.
Cobalt is a weakly reducing metal that is protected from oxidation by a
passivatingPassivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...
oxide film. It is attacked by halogens and sulfur. Heating in oxygen produces
Co3O4Cobalt oxide is inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid...
which loses oxygen at 900 °C to give the
monoxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
CoO.
Compounds
{{Category see also|Cobalt compounds}}
Common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +4 are also known. A common oxidation state for simple compounds is +2. Cobalt(II) salts form the red-pink [Co(H
2O)
6]
2+ complex in aqueous solution. Addition of chloride gives the intensely blue .
Oxygen and chalcogen compounds
Several
oxideAn oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s of cobalt are known. Green
cobalt(II) oxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
(CoO) has
rocksaltIn crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....
structure. It is readily oxidized with water and oxygen to brown cobalt(III) hydroxide (Co(OH)
3). At temperatures of 600–700 °C, CoO oxidizes to the blue
cobalt(II,III) oxideCobalt oxide is inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid...
(Co
3O
4), which has a
spinelSpinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
structure. Black
cobalt(III) oxideCobalt oxide is the inorganic compound with the formula Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co salts such as cobalt nitrate with an aqueous solution of sodium hypochlorite gives a...
(Co
2O
3) is also known. Cobalt oxides are antiferromagnetic at low
temperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
: CoO (
Neel temperatureThe Néel temperature or magnetic ordering temperature , TN, is the temperature above which an antiferromagnetic material becomes paramagnetic—that is, the thermal energy becomes large enough to destroy the macroscopic magnetic ordering within the material....
291 K) and Co
3O
4 (Neel temperature: 40 K), which is analogous to
magnetiteMagnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
(Fe
3O
4), with a mixture of +2 and +3 oxidation states.
The principal
chalcogenThe chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...
ides of cobalt include the black cobalt(II) sulfides, CoS
2, which adopts a
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
-like structure, and Co
2S
3.
PentlanditePentlandite is an iron-nickel sulfide, 9S8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt.Pentlandite forms isometric crystals, but is normally found in massive granular aggregates. It is brittle with a hardness of 3.5 - 4 and specific gravity of 4.6 - 5.0 and...
(Co
9S
8) is metal-rich.
Halides
The four dihalides of cobalt(II) are known:
cobalt(II) fluorideCobalt fluoride is a chemical compound with the formula . It is a pink crystalline solid compound. The formula is given for both the red tetragonal crystal, , and the tetrahydrate red orthogonal crystal, . CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it...
(CoF
2, pink),
cobalt(II) chlorideCobalt chloride is an inorganic compound of cobalt and chloride, with the formula CoCl2. It is usually supplied as the hexahydrate CoCl2·6H2O, which is one of the most commonly used cobalt compounds in the laboratory. The hexahydrate is deep purple in color, whereas the anhydrous form is sky blue...
(CoCl
2, blue),
cobalt(II) bromideCobalt bromide is an inorganic compound used primarily as a catalyst in some processes.-Properties:When anhydrous, cobalt bromide appears as green crystals. The hexahydrate loses four waters of crystallization molecules at 100°C forming the dihydrate:Further heating to 130°C Produces the anhydrous...
(CoBr
2, green),
cobalt(II) iodideCobalt iodide or cobaltous iodide is the inorganic compound composed with the formula Co I2. The two forms of CoI2 and the hydrated form are the principal iodides of cobalt.-Synthesis and structure:...
(CoI
2, blue-black). These halides exist as anhydrous and hydrates. Whereas the anhydrous dichloride is blue, the hydrate is red.
The reduction potential for the reaction
- + →
is +1.92 V, beyond that for
chlorineChlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
to chloride, +1.36 V. As a consequence cobalt(III) and chloride would result in the cobalt(III) being reduced to cobalt(II). Because the reduction potential for fluorine to fluoride is so high, +2.87 V, cobalt(III) fluoride is one of the few simple stable cobalt(III) compounds. Cobalt(III) fluoride, which is used in some fluorination reactions, reacts vigorously with water.
Coordination compounds
As for all metals, molecular compounds of cobalt are classified as coordination complexes, that is molecules or ions that contain cobalt linked to several
ligandIn coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s. The principles of
electronegativityElectronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
and
hardness–softnessThe HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
of a series of ligands can be used to explain the usual oxidation state of the cobalt. For example Co
+3 complexes tend to have
ammineIn coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelled with a single "m"...
ligands. As phosphorus is softer than nitrogen, phosphine ligands tend to feature the
softerThe HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
Co
2+ and Co
+, an example being tris(triphenylphosphine)cobalt(I) chloride ((P(C
6H
5)
3)
3CoCl). The more electronegative (and harder) oxide and fluoride can stabilize Co
4+ derivatives, e.g. caesium hexafluorocobaltate (Cs
2CoF
6) and potassium percobaltate (K
3CoO
4).
Alfred WernerAlfred Werner was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry...
, a Nobel-prize winning pioneer in coordination chemistry, worked with compounds of
empirical formulaIn chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic...
CoCl
3(NH
3)
6. One of the isomers determined was
cobalt(III) hexammine chlorideHexamminecobalt chloride is the chemical compound with the formula [Co6]Cl3. This coordination compound is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner. This salt consists of [Co6]3+ trications with three Cl− anions...
. This coordination complex, a "typical" Werner-type complex, consists of a central cobalt atom coordinated by six
ammineIn coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelled with a single "m"...
ligands orthogonal to each other and three
chlorideThe chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
counteranions. Using chelating ethylenediamine ligands in place of ammonia gives
tris(ethylenediamine)cobalt(III) chlorideTriscobalt chloride is a coordination complex with the formula [Co3]Cl3 . This complex was important in the history of coordination chemistry because of its stability and its stereochemistry. Many different salts have been described...
([Co(en)
3]Cl), which was one of the first coordination complexes that was resolved into
optical isomersA chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
. The complex exists as both either right- or left-handed forms of a "three-bladed propeller". This complex was first isolated by Werner as yellow-gold needle-like crystals.
Organometallic compounds
{{Main|Organocobalt chemistry}}
CobaltoceneCobaltocene, known also as biscobalt or even "bis Cp cobalt", is an organocobalt compound with the formula Co2. It is a dark purple solid that sublimes readily slightly above room temperature. Cobaltocene was discovered shortly after ferrocene, the first metallocene...
is a structural analog to
ferroceneFerrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds...
, where cobalt substitutes for iron. Cobaltocene is sensitive to oxidation, much more than ferrocene. Cobalt carbonyl (Co
2(CO)
8) is a
catalystCatalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
in
carbonylationCarbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry.-Organic chemistry:...
reactions.
Vitamin B12Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
(see below) is an organometallic compound found in nature and is the only
vitaminA vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
to contain a metal atom.
Isotopes
{{Main|Isotopes of cobalt}}
59Co is the only stable cobalt
isotopeIsotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
and the only isotope to exist in nature. 22 radioisotopes have been characterized with the most stable being
60Co with a
half-lifeHalf-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 5.2714 years,
57Co with a half-life of 271.79 days,
56Co with a half-life of 77.27 days, and
58Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are shorter than 18 hours, and the majority of these are shorter than 1 second. This element also has 4 meta states, all of which have half-lives shorter than 15 minutes.
The isotopes of cobalt range in
atomic weightAtomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
from 50
uThe unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
(
50Co) to 73 u (
73Co). The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope,
59Co, is
electron captureElectron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
and the primary mode of decay for those of greater than 59 atomic mass units is
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
. The primary
decay productIn nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...
s before
59Co are element 26 (
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
) isotopes and the primary products after are element 28 (nickel) isotopes.
History
Cobalt compounds have been used for centuries to impart a rich blue color to
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
,
glazesGlaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
and
ceramicsIn art history, ceramics and ceramic art mean art objects such as figures, tiles, and tableware made from clay and other raw materials by the process of pottery. Some ceramic products are regarded as fine art, while others are regarded as decorative, industrial or applied art objects, or as...
. Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of
PompeiiThe city of Pompeii is a partially buried Roman town-city near modern Naples in the Italian region of Campania, in the territory of the comune of Pompei. Along with Herculaneum, Pompeii was destroyed and completely buried during a long catastrophic eruption of the volcano Mount Vesuvius spanning...
(destroyed in 79 AD), and in China dating from the
Tang dynastyThe Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
(618–907 AD) and the
Ming dynastyThe Ming Dynasty, also Empire of the Great Ming, was the ruling dynasty of China from 1368 to 1644, following the collapse of the Mongol-led Yuan Dynasty. The Ming, "one of the greatest eras of orderly government and social stability in human history", was the last dynasty in China ruled by ethnic...
(1368–1644 AD).
Cobalt has been used to color glass since the
Bronze AgeThe Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...
. The excavation of the
Uluburun shipwreckThe Uluburun Shipwreck is a Late Bronze Age shipwreck dated to the late 14th century BCE, discovered off Uluburun situated about 6 miles southeast of Kaş, in south-western Turkey...
yielded an ingot of blue glass, which was cast during the 14th century BC. Blue glass items from Egypt are colored with copper, iron, or cobalt. The oldest cobalt-colored glass was from the time of the
Eighteenth dynastyThe eighteenth dynasty of ancient Egypt is perhaps the best known of all the dynasties of ancient Egypt...
in
EgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
(1550–1292 BC). The location where the cobalt compounds were obtained is unknown.
The word
cobalt is derived from the German
{{lang|mhd|kobalt}}, from
koboldThe kobold is a sprite stemming from Germanic mythology and surviving into modern times in German folklore. Although usually invisible, a kobold can materialise in the form of an animal, fire, a human being, and a candle. The most common depictions of kobolds show them as humanlike figures the size...
meaning "goblin", a superstitious term used for the
oreAn ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
of cobalt by miners. The first attempts at smelting these ores to produce metals such as copper or nickel failed, yielding simply powder (cobalt(II) oxide) instead. Also, because the primary ores of cobalt always contain
arsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, smelting the ore oxidized the arsenic content into the highly toxic and volatile arsenic oxide, which also decreased the reputation of the ore for the miners.
Swedish chemist
Georg Brandt-External links:** by Uno Boklund in: Charles C. Gillispie, ed., Dictionary of Scientific Biography , vol. 2, pages 421-422....
(1694–1768) is credited with discovering cobalt circa 1735, showing it to be a new previously unknown element different from bismuth and other traditional metals, and calling it a new "semi-metal." He was able to show that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period, during which all the known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers.
During the 19th century, a significant part of the world's production of
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
(a dye made with cobalt compounds and alumina) and
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
(
cobalt glassCobalt glass is a deep blue colored glass prepared by adding cobalt compounds to the molten glass. It is appreciated for its attractive color. It is also used as an optical filter in flame tests to filter out the yellow flame caused by the contamination of sodium, and expand the ability to see...
powdered for use for pigment purposes in ceramics and painting) was carried out at the Norwegian
BlaafarveværketBlaafarveværket in Modum, Norway, founded by King Christian VII of Denmark-Norway in the 1770s, became the largest industrial company of the country in the mid-19th century. The works mined cobalt ore and manufactured by smelting blue cobalt glass and cobalt blue pigment...
. The first mines for the production of
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
in the 16th to 18th century were located in Norway,
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
,
SaxonyThe Free State of Saxony is a landlocked state of Germany, contingent with Brandenburg, Saxony Anhalt, Thuringia, Bavaria, the Czech Republic and Poland. It is the tenth-largest German state in area, with of Germany's sixteen states....
and Hungary. With the discovery of cobalt ore in
New CaledoniaNew Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
in 1864 the mining of cobalt in Europe declined. With the discovery of ore deposits in
OntarioOntario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
,
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
in 1904 and the discovery of even larger deposits in the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
in the Congo in 1914 the mining operations shifted again. With the
Shaba conflictShaba II was an invasion of the Shaba separatist movement FNLC into the Zairian province of Shaba on 11 May 1978. The FNLC had its bases in eastern Angola and probably had the support of the Angolan government...
starting in the 1978 the main source for cobalt the copper mines of
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
nearly stopped their production. The impact on the world cobalt economy from this conflict was smaller than expected, because industry established effective ways for recycling cobalt materials and in some cases was able to change to cobalt-free alternatives.
In 1938, John Livingood and
Glenn T. SeaborgGlenn Theodore Seaborg was an American scientist who won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements", contributed to the discovery and isolation of ten elements, and developed the actinide concept, which led to the current arrangement of the...
discovered cobalt-60. This isotope was famously used at
Columbia UniversityColumbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
in the 1950s to establish
parityIn physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...
violation in radioactive
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
.
Occurrence
The stable form of cobalt is created in
supernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
s via the
r-processThe r-process is a nucleosynthesis process, likely occurring in core-collapse supernovae responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron. The process entails a succession of rapid neutron captures on seed nuclei, typically Ni-56,...
. It comprises
0.0029% of the Earth's crustThe abundance of a chemical element measures how relatively common the element is, or how much of the element is present in a given environment by comparison to all other elements...
and is one of the first
transition metalThe term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
series.
Cobalt occurs in copper and nickel minerals and in combination with
sulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and
arsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
in the sulfidic
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
(CoAsS),
saffloriteSafflorite is a rare cobalt iron arsenide mineral with formula: As2. Pure safflorite would be just CoAs2, but iron is virtually always present. Safflorite is a member of the three-way substitution series of arsenides known as the löllingite or löllingite group...
(CoAs
2) and
skutteruditeSkutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...
(CoAs
3) minerals. The mineral
cattieriteCattierite is a mineral found in the Democratic Republic of Congo. It was discovered together with Vaesite by Johannes F. Vaes, a Belgian mineralologist and named after Felicien Cattier, Chairman of the Board, Union Miniere du Haut Katanga....
is similar to
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
and occurs together with
vaesiteVaesite is a mineral found together with cattierite in the Democratic Republic of Congo. It is named after Johannes F. Vaes, a Belgian mineralologist.-References:**...
in the copper deposits of the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
. Upon contact with the atmosphere,
weatheringWeathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
occurs and the sulfide minerals oxidize to form pink
erythrite ("cobalt glance": Co
3(AsO
4)
2·8H
2O) and
sphaerocobaltiteSphaerocobaltite is a cobalt carbonate mineral with chemical composition CoCO3. In its pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown.-Further reading:*...
(CoCO
3).
Cobalt is not found as a
native metalA native metal is any metal that is found in its metallic form, either pure or as an alloy, in nature. Metals that can be found as native deposits singly and/or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, nickel, selenium, tantalum, tellurium,...
but is mainly obtained as a
by-productA by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....
of nickel and
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
mining activities. The main ores of cobalt are
cobaltiteCobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....
,
erythrite,
glaucodotGlaucodot is a cobalt iron arsenic sulfide mineral with formula: AsS. The cobalt:iron ratio is typically 3:1 with minor nickel substituting. It forms a series with arsenopyrite . It is an opaque grey to tin-white typically found as massive forms without external crystal form. It crystallizes in the...
and
skutteruditeSkutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...
.
Production
{{See also|Cobalt extraction techniques}}
In 2005, the copper deposits in the
Katanga ProvinceKatanga Province is one of the provinces of the Democratic Republic of the Congo. Between 1971 and 1997, its official name was Shaba Province. Under the new constitution, the province was to be replaced by four smaller provinces by February 2009; this did not actually take place.Katanga's regional...
(former Shaba province) of the
Democratic Republic of the CongoThe Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
were the top producer of cobalt with almost 40% world share, reports the
British Geological SurveyThe British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
. The political situation in the Congo influences the price of cobalt significantly.
The Mukondo Mountain project, operated by the
Central African Mining and Exploration CompanyThe Central African Mining and Exploration Company was a mining company active in the Katanga Province of the Democratic Republic of the Congo and in other parts of Africa. It was acquired by ENRC in 2009.-Early years:...
in Katanga, may be the richest cobalt reserve in the world. It is estimated to be able to produce about one third of total global production of cobalt in 2008.
In July 2009 CAMEC announced a long term agreement under which CAMEC would deliver its entire annual production of cobalt in concentrate from Mukondo Mountain to Zhejiang Galico Cobalt & Nickel Materials of China.
Several methods exist for the separation of cobalt from copper and nickel. They depend on the concentration of cobalt and the exact composition of the used ore. One separation step involves
froth flotationFroth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries...
, in which surfactants bind to different ore components, leading to an enrichment of cobalt ores. Subsequent
roastingRoasting is a step in the processing of certain ores. More specifically, roasting is a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component. Often before roasting, the ore has already been partially purified, e.g. by froth...
converts the ores to the cobalt sulfate, whereas the copper and the iron are oxidized to the oxide. The
leachingLeaching is a widely used extractive metallurgy technique which converts metals into soluble salts in aqueous media. Compared to pyrometallurgical operations, leaching is easier to perform and much less harmful, because no gaseous pollution occurs...
with water extracts the sulfate together with the
arsenateThe arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....
s. The residues are further leached with
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
yielding a solution of copper sulfate. Cobalt can also be leached from the slag of the copper smelter.
The products of the above-mentioned processes are transformed into the cobalt oxide (Co
3O
4). This oxide is reduced to the metal by the
aluminothermic reactionAluminothermic reactions are exothermic chemical reactions using aluminium as the reducing agent at high temperature. The most prominent example is the thermite reaction between aluminium and iron oxides:-History:...
or reduction with carbon in a
blast furnaceA blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...
.
Alloys
Cobalt-based
superalloyA superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys typically have a matrix with an austenitic face-centered cubic crystal structure. ...
s consume most of the produced cobalt. The temperature stability of these alloys makes them suitable for use in turbine blades for gas
turbineA turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
s and jet
aircraftAn aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
engineAn engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
s, though nickel-based
single crystalA single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...
alloys surpass them in this regard. Cobalt-based alloys are also
corrosionCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
and wear-resistant. This makes them useful in the medical field, where cobalt is often used (along with
titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
) for orthopedic
implantAn implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, which is a transplanted biomedical tissue...
s that do not wear down over time. The development of the wear-resistant cobalt alloys started in the first decade of the 19th century with the
stelliteStellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon...
alloys, which are cobalt-chromium alloys with varying tungsten and carbon content. The formation of chromium and tungsten carbides makes them very hard and wear resistant. Special cobalt-
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
-
molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
alloys like
VitalliumVitallium is a trademark for an alloy of 60% cobalt, 20% chromium, 5% molybdenum, and other substances. The alloy is used in dentistry and artificial joints, because of its light weight and resistance to corrosion. It is also used for components of turbochargers because of its thermal resistance....
are used for prosthetic parts such as hip and knee replacements. Cobalt alloys are also used for dental prosthetics, where they are useful to avoid allergies to nickel. Some
high speed steelHigh speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
s also use cobalt to increase heat and wear-resistance. The special alloys of aluminium, nickel, cobalt and iron, known as
AlnicoAlnico is an acronym referring to iron alloys which in addition to iron are composed primarily of aluminium , nickel and cobalt , hence al-ni-co, with the addition of copper, and sometimes titanium. Alnico alloys are ferromagnetic, with a high coercivity and are used to make permanent magnets...
, and of samarium and cobalt (
samarium-cobalt magnetA samarium–cobalt magnet, a type of rare earth magnet, is a strong permanent magnet made of an alloy of samarium and cobalt. They were developed in the early 1970s. They are generally the second-strongest type of magnet made, less strong than neodymium magnets, but have higher temperature ratings...
) are used in permanent magnets.
[{{cite journal|title = Reproducing the Properties of Alnico Permanent Magnet Alloys with Elongated Single-Domain Cobalt-Iron Particles|journal = Journal Applied Physics|volume = 28|issue = 344|year = 1957|doi = 10.1063/1.1722744|first = F. E.|last = Luborsky|coauthors = Mendelsohn, L. I.; Paine, T. O.|page = 344|bibcode = 1957JAP....28..344L }}] It is also alloyed with 95%
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
for jewelry purposes, yielding an alloy that is suitable for fine detailed casting and is also slightly magnetic.
Batteries
Lithium cobalt oxideLithium cobalt oxide is a chemical compound commonly used in the positive electrodes of lithium-ion batteries. The structure of LiCoO2 is known theoretically and has been confirmed with techniques like x-ray diffraction, electron microscopy, neutron powder diffraction, and EXAFS: it consists of...
(LiCoO
2) is widely used in
lithium ion batteryA lithium-ion battery is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types...
cathodes. The material is composed of cobalt oxide layers in which the lithium is
intercalatedIn chemistry, intercalation is the reversible inclusion of a molecule between two other molecules . Examples include DNA intercalation and graphite intercalation compounds.- DNA intercalation :...
. During discharging the lithium intercalated between the layers is set free as lithium ion.
Nickel-cadmiumThe nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
(NiCd) and
nickel metal hydrideA nickel–metal hydride cell, abbreviated NiMH, is a type of rechargeable battery similar to the nickel–cadmium cell. The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd cells, the positive electrode is nickel oxyhydroxide...
(NiMH) batteries also contain significant amounts of cobalt; the cobalt improves the oxidation capabilities of nickel in the battery.
Catalysis
Several cobalt compounds are used in chemical reactions as oxidation catalysts. Cobalt acetate is used for the conversion of
xyleneXylene encompasses three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- , meta- , and para- , which specify to which carbon atoms the two methyl groups are attached...
to
terephthalic acidTerephthalic acid is the organic compound with formula C6H42. This colourless solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several billion kilograms are produced annually...
, the precursor to the bulk polymer
polyethylene terephthalatePolyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
. Typical catalysts are the cobalt carboxylates (known as cobalt soaps). They are also used in paints, varnishes, and inks as "drying agents" through the oxidation of drying oils. The same carboxylates are used to improve the adhesion of the steel to rubber in steel-belted radial tires.
Cobalt-based catalysts are also important in reactions involving
carbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
.
Steam reformingFossil fuel reforming is a method of producing hydrogen or other useful products from fossil fuels such as natural gas. This is achieved in a processing device called a reformer which reacts steam at high temperature with the fossil fuel. The steam methane reformer is widely used in industry to...
, useful in
hydrogen productionHydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...
, uses cobalt oxide-base catalysts. Cobalt is also a catalyst in the
Fischer-Tropsch processThe Fischer–Tropsch process is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic...
, used in the
hydrogenationHydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
of carbon monoxide into liquid fuels. The
hydroformylationHydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
of
alkeneIn organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s often rely on cobalt octacarbonyl as the catalyst, although such processes have been partially displaced by more efficient iridium- and rhodium-based catalysts, e.g. the
Cativa processThe Cativa process is a method for the production of acetic acid by the carbonylation of methanol. The technology, which is similar to the Monsanto process, was developed by BP Chemicals and is under license by BP Plc...
.
The
hydrodesulfurizationHydrodesulfurization is a catalytic chemical process widely used to remove sulfur from natural gas and from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils...
of
petroleumPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
uses a catalyst derived from cobalt and molybdenum. This process helps to rid petroleum of sulfur impurities that interfere with the refining of liquid fuels.
Pigments and coloring
Before the 19th century, the predominant use of cobalt was as pigment. Since the Middle Ages, it has been involved in the production of
smaltSmalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...
, a blue colored glass. Smalt is produced by melting a mixture of the roasted mineral
smaltiteSmaltite is a variety of the mineral skutterudite consisting of cobalt iron nickel arsenide: As2.Smaltite crystallizes in the cubic system with the same hemihedral symmetry as pyrite; crystals have usually the form of cubes or cubo-octahedra, but are imperfectly developed and of somewhat rare...
,
quartzQuartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and
potassium carbonatePotassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
, yielding a dark blue silicate glass which is ground after the production. Smalt was widely used for the coloration of glass and as pigment for paintings. In 1780,
Sven RinmanSven Rinman was a Swedish chemist and mineralogist who discovered the pigment cobalt green, sometimes also called Rinman's green. He had a great influence on mining and the steel production in Sweden.-Life and work:...
discovered
cobalt greenCobalt green, sometimes known as Rinman's green or Zinc Green, is a translucent green pigment made by heating a mixture of cobalt oxide and zinc oxide. Sven Rinman, a Swedish chemist, discovered this compound in 1780. Although it is stable and can be safely mixed with other pigments, it is rarely...
and in 1802
Louis Jacques ThénardLouis Jacques Thénard , was a French chemist.His father, a poor peasant, managed to have him educated at the academy of Sens, and sent him at the age of sixteen to study pharmacy in Paris. There he attended the lectures of Antoine François Fourcroy and Louis Nicolas Vauquelin...
discovered
cobalt blueCobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...
. The two varieties of cobalt blue, cobalt aluminate and cobalt green (a mixture of
cobalt(II) oxideCobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...
and
zinc oxideZinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...
), were used as pigments for paintings because of their superior stability.
Radioisotopes
Cobalt-60 (Co-60 or
60Co) is useful as a gamma ray source because it can be produced in predictable quantity and high activity by bombarding cobalt with
neutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s. It produces two
gamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s with energies of 1.17 and 1.33
MeVMeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...
.
Its uses include
external beam radiotherapyExternal beam radiotherapy or teletherapy is the most common form of radiotherapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body...
, sterilization of medical supplies and medical waste, radiation treatment of
foods for sterilizationFood irradiation is the process of exposing food to ionizing radiation to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration...
(cold
pasteurizationPasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
), industrial
radiographyRadiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
(e.g. weld integrity radiographs), density measurements (e.g. concrete density measurements), and tank fill height switches. The metal has the unfortunate habit of producing a fine dust, causing problems with radiation protection. Cobalt from radiotherapy machines has been a serious hazard when not disposed of properly, and one of the worst radiation contamination accidents in North America occurred in 1984, after a discarded radiotherapy unit containing cobalt-60 was mistakenly disassembled in a junkyard in Juarez, Mexico.
Cobalt-60 has a radioactive half-life of 5.27 years. This decrease in activity requires periodic replacement of the sources used in radiotherapy and is one reason why cobalt machines have been largely replaced by
linear acceleratorA linear particle accelerator is a type of particle accelerator that greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline; this method of particle acceleration was invented...
s in modern radiation therapy.
Cobalt-57 (Co-57 or
57Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for
vitamin B{{ssubVitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
uptake, and for the
Schilling testThe Schilling test is a medical investigation used for patients with vitamin B deficiency. The purpose of the test is to determine whether the patient has pernicious anemia.It is named for Robert F. Schilling.-Process:The Schilling test has multiple stages...
. Cobalt-57 is used as a source in Mössbauer spectroscopy and is one of several possible sources in
X-ray fluorescenceX-ray fluorescence is the emission of characteristic "secondary" X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays...
devices.
Nuclear weapon designNuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three basic design types...
s could intentionally incorporate
59Co, some of which would be activated in a
nuclear explosionA nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...
to produce
60Co. The
60Co, dispersed as
nuclear falloutFallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
, creates what is sometimes called a
cobalt bombA cobalt bomb is a theoretical type of "salted bomb": a nuclear weapon intended to contaminate an area by radioactive material, with a relatively small blast....
.
Other uses
Other uses of cobalt are in
electroplatingElectroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...
, owing to its attractive appearance, hardness and resistance to oxidation, and as ground coats for
porcelainPorcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...
enamelVitreous enamel, also porcelain enamel in U.S. English, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C...
s.
Biological role
Cobalt is essential to all
animalAnimals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s, including humans. It is a key constituent of cobalamin, also known as
vitamin B{{ssubVitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
, which is the primary biological reservoir of cobalt as an "ultratrace" element. Bacteria in the guts of
ruminantA ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
animals convert cobalt salts into vitamin B{{ssub|12}}, a compound which can only be produced by bacteria. The minimum presence of cobalt in soils therefore markedly improves the health of
grazingGrazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
animals, and an uptake of 0.20 mg/kg a day is recommended. Non-ruminant herbivores produce
vitamin B{{ssubVitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
from bacteria in their colons, from which the vitamin cannot be absorbed, and thus some of them ingest feces to obtain the nutrient. Animals that do not follow these methods of getting
vitamin B{{ssubVitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
from their own gastrointestinal bacteria must obtain the vitamin from animal products in their diet, and they cannot benefit from ingesting simple cobalt salts.
The cobalamin-based proteins use
corrinCorrin is an heterocyclic compound. It is the parent macrocycle related to substituted derivative that is found in vitamin B12. Its name reflects that it is the "core" of vitamin B12 .-Coordination chemistry:...
to hold the cobalt. Coenzyme B
12 features a reactive C-Co bond, which participates in its reactions. In humans, B
12 exists with two types of
alkylAlkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...
ligand:
methylMethyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...
and adenosyl. MeB
12 promotes methyl (-CH
3) group transfers. The adenosyl version of B
12 catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. Methylmalonyl coenzyme A mutase (MUT) converts MMl-CoA to
Su-CoASuccinyl-Coenzyme A, abbreviated as Succinyl-CoA or SucCoA, is a combination of succinic acid and coenzyme A.-Source:It is an important intermediate in the citric acid cycle, where it is synthesized from α-Ketoglutarate by α-ketoglutarate dehydrogenase through decarboxylation...
, an important step in the extraction of energy from proteins and fats.
Although far less common than other metalloproteins (e.g. those of zinc and iron), cobaltoproteins are known aside from B
12. These proteins include
methionine aminopeptidase 2Methionine aminopeptidase 2 is an enzyme that in humans is encoded by the METAP2 gene.- Function :This gene is a member of the methionyl aminopeptidase family and encodes a protein that binds 2 cobalt or manganese ions...
an enzyme that occurs in humans and other mammals which does not use the corrin ring of B
12, but binds cobalt directly. Another non-corrin cobalt enzyme is
nitrile hydrataseIn enzymology, nitrile hydratases are mononuclear iron or non-corrinoid cobalt enzymes that catalyse the hydration of diverse nitriles to their corresponding amidesR-C≡N + H2O → R-CNH2-Metal cofactor:...
, an enzyme in bacteria that are able to metabolize
nitrileA nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
s.
Precautions
{{Main|Cobalt poisoning}}
Cobalt is an essential element for life in minute amounts. The LD
50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg/kg. Thus, for a 100 kg person the LD
50 would be about 20 grams.
After
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
and
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
, cobalt is a major cause of
contact dermatitisAllergic contact dermatitis is a form of contact dermatitis that is the manifestation of an allergic response caused by contact with a substance....
. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to
cardiomyopathyCardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...
, which came to be known as
beer drinker's cardiomyopathy.
External links
{{Commons|Cobalt}}
{{Wiktionary|cobalt}}
{{Clear}}
{{Compact periodic table}}
{{Cobalt compounds}}
{{Good Article}}