Chemical Properties
Cobalt is a silvery, bluish-white, odorless, and magnetic metal. The fume and dust of cobalt
metal is odorless and black. The appearance and odor of cobalt compounds and their dusts
and fumes vary with the compound. Cobalt metal in powdered form is incompatible with
fused ammonium nitrate, hydrozinium nitrate, and strong oxidizing agents and should be
avoided. It ignites on contact with bromide pentafl uoride. Powdered cobalt ignites spontaneously in air. Exposure to cobalt metal fume and dust can occur through inhalation,
ingestion, and eye or skin contact.
General Description
A black powder.
Reactivity Profile
Pyrophoric COBALT(7440-48-4) is a reducing agent. Decomposes acetylene in the cold as the metal becomes incandescent [Mellor 14:513(1946-1947]. Incompatible with oxidizing agents such as ammonium nitrate, bromine pentafluoride, and nitryl fluoride.
Air & Water Reactions
Burns brilliantly when exposed to air [Mellor 14:453(1946-1947)]. Insoluble in water.
Hazard
A possible carcinogen. Toxic by inhalation.
Dust is flammable. Asthma, myocardial effects, and
pulmonary function impairment.
Health Hazard
Acute exposure to cobalt metal, dust, and fume is characterized by irritation of the eyes
and, to a lesser extent, irritation of the skin. In sensitized individuals, exposure causes an
asthma-like attack, with wheezing, bronchospasm, and dyspnea. Ingestion of cobalt may
cause nausea, vomiting, diarrhea, and a sensation of heat.
Human exposures to cobalt and cobalt compounds cause cough, tight chest, pain in chest
on coughing, dyspnea, malaise, ache, chills, sweating, shivering, and aching pain in back
and limbs. After further days of exposures to high concentrations of cadmium, the worker
develops more severe pulmonary responses such as severe dyspnea, wheezing, chest pain
and precordial constriction, persistent cough, weakness and malaise, anorexia, nausea,
diarrhea, nocturia, abdominal pain, diffuse nodular fi brosis, respiratory hypersensitivity, asthma, abdominal pain, cardiomyopathy, lung damage, hemoptysis, prostration, and
death.
Cobalt metal, dust, and fume are pulmonary toxins and respiratory and skin sensitizers. Inhalation of cobalt metal fume and dust may cause interstitial fi brosis, interstitial
pneumonitis, myocardial and thyroid disorders, and sensitization of the respiratory tract
and skin. Chronic cobalt poisoning may also produce polycythemia and hyperplasia of the
bone marrow. Myocardial disorders have also been observed in cobalt production workers. Chronic exposure to cobalt metal, dust, or fume may cause respiratory or dermatologic
signs and symptoms. Following skin sensitization, contact with cobalt causes eruptions of
dermatitis in creases and on frictional surfaces of the arms, legs, and neck. Chronic cobalt
poisoning may cause polycythemia, hyperplasia of the bone marrow and thyroid gland,
pericardial effusion, and damage to the alpha cells of the pancreas.
Potential Exposure
Possible risk of forming tumors, Suspected reprotoxic hazard. Nickel-aluminumcobalt alloys are used for permanent magnets. Alloys with nickel, aluminum, copper, beryllium, chromium, and molybdenum are used in the electrical, automobile, and aircraft industries. Cobalt is added to tool steels to improve their cutting qualities and is used as a binder in the manufacture of tungsten carbide tools. Various cobalt compounds are used as pigments in enamels, glazes, and paints; as catalysts in afterburners; and in the glass, pottery, photographic, electroplating industries. Radioactive cobalt (60Co) is used in the treatment of cancer. Cobalt has been added to beer to promote formation of foam but cobalt acts with alcohol to produce severe cardiac effects at concentrations as low as 1.2-1.5 mg/L of beer. Cobalt is part of the vitamin B12 molecule and as such is an essential nutrient. The requirement of humans for cobalt in the form of vitamin B12 is about 0.13 μg/day.
Fire Hazard
Literature sources indicate that the dust of this chemical is flammable.
First aid
If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. Medical observation is recommended for 24 to 48 hours after breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a drug or other inhalation therapy
Shipping
UN3189 Metal powder, self-heating, n.o.s., Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material
Description
Cobalt was discovered by George Brandt in 1737. Cobalt exists
in valence states from 0 to 5, with the most stable (+2 and +3)
being the most common. Although there is only one stable
isotope of cobalt, there are a number of unstable isotopes. Two
of these, cobalt-60 and cobalt-57, are in use commercially.
Cobalt-60 is used for cancer treatment and food irradiation.
Cobalt-57 has research applications.
Waste Disposal
Cobalt metal may be recovered from scrap and cobalt compounds from spent catalysts as alternatives to disposal.
Isotopes
There are 33 isotopes of cobalt, ranging from Co-48 to Co-75, with half-livesranging from a few nanoseconds to 5.272 years for cobalt-60. Cobalt-59 is the onlystable isotope that constitutes almost all (roughly 100%) of the element’s natural presence on Earth. All the other isotopes are radioactive and are created artificially in nuclearreactors or nuclear explosions.
Origin of Name
Cobalt was given the name kobolds (or kolalds, or kololos) by German
miners. It means “goblin” (see “History” for more on this story).
Occurrence
Cobalt is the 32nd most abundant element on Earth even though it makes up only 0.003%of the Earth’s crust. It is not found in the free metallic state, despite being widely distributedin igneous rocks as minerals. Its two most common mineral ores are cobaltite (CoAsS) anderythrite [Co3(AsO4)2]. These ores are placed in blast furnaces to produce cobalt arsenide(Co2As), which is then treated with sulfuric acid to remove the arsenic. Finally, the productcobalt tetraoxide (Co3O4) is reduced by heat with carbon (Co3O4 + C → 3Co + 2CO2), resulting in cobalt metal.Cobalt is also found in seawater, meteorites, and other ores such as linnaeite, chloanthite,and smaltite, and traces are found mixed with the ores of silver, copper, nickel, zinc, andmanganese. Cobalt ores are found in Canada and parts of Africa, but most of the cobalt usedin the United States is recovered as a by-product of the mining, smelting, and refining of theores of iron, nickel, lead, copper, and zinc.
Characteristics
Cobalt has the highest Curie point of any metal or alloy of cobalt. The Curie point is thetemperature at which an element will lose its magnetism before it reaches its melting point.Cobalt’s Curie point is 1,121°C, and its melting point is 1,495°C. About 25% of all cobaltmined in the world is used as an alloy with other metals. The most important is the alloyalnico, which consists of nickel, aluminum, and cobalt. Alnico is used to make powerful permanent magnets with many uses, such as CT, PET, and MRI medical instruments. It is alsoused for electroplating metals to give a fine surface that resists oxidation.
Definition
A lustrous silveryblue
hard ferromagnetic transition metal
occurring in association with nickel. It is
used in alloys for magnets, cutting tools,
and electrical heating elements and in catalysts
and some paints.
Definition
ChEBI: A cobalt group element atom that has atomic number 27.
Definition
cobalt: Symbol Co. A light-greytransition element; a.n. 27; r.a.m.58.933; r.d. 8.9; m.p. 1495°C; b.p.2870°C. Cobalt is ferromagneticbelow its Curie point of 1150°C.Small amounts of metallic cobalt arepresent in meteorites but it is usuallyextracted from ore deposits workedin Canada, Morocco, and Za?re. It ispresent in the minerals cobaltite,smaltite, and erythrite but also associatedwith copper and nickel as sulphidesand arsenides. Cobalt ores areusually roasted to the oxide and thenreduced with carbon or water gas.Cobalt is usually alloyed for use. Alnicois a well-known magnetic alloyand cobalt is also used to make stainlesssteels and in high-strength alloysthat are resistant to oxidation at hightemperatures (for turbine blades andcutting tools).
The metal is oxidized by hot airand also reacts with carbon, phosphorus,sulphur, and dilute mineralacids. Cobalt salts, usual oxidationstates II and III, are used to give abrilliant blue colour in glass, tiles,and pottery. Anhydrous cobalt(II)chloride paper is used as a qualitativetest for water and as a heat-sensitiveink. Small amounts of cobalt salts areessential in a balanced diet for mam-mals. Artificiallyproduced cobalt–60 is an importantradioactive tracer andcancer-treatment agent. The elementwas discovered by Georg Brandt(1694–1768) in 1737.
Reactions
Cobalt absorbs very little hydrogen even at high temperatures and nitrogen is practically
insoluble up to 1200°C. Finely divided cobalt is pyrophoric in air, but the massive metal
is scarcely attacked below 300°C. The oxide scale on cobalt heated in air or oxygen up to
900° consists of an outside layer of CO3O4 and a layer of CoO next to the metal ; above
900°, Co3O4 decomposes and the scale consists of CoO only. Cobalt reacts with many
non-metals when heated, e.g. the halogens, boron, sulphur, phosphorus, arsenic and
antimony, the reactions often proceeding with incandescence. Fluorine forms CoF3, while
the other halogens give the cobalt(II) halide.
Brand name
C.i. 77320;Cobalt-59;Impromin;Inter-con;Kometileneamin;Levacide-c;Orkomin;Panacur;Sofracaps;Tasvite;Trelenium.
World Health Organization (WHO)
WHO Comment(non-radioactive forms): The World Health Organization has no information further to the
above regarding preparations containing cobalt or to indicate that they are still
commercially manufactured.
Flammability and Explosibility
Notclassified
Agricultural Uses
Cobalt (Co), a metallic element with an atomic weight of 58.94, is one of the transition elements belonging to the Group 9 (formerly Group VIII ) of the Periodic Table. However, in extremely low concentrations ranging from 0.1 to 10parts per billion (ppb), cobalt have been observed to improve growth, transpiration and photosynthesis of cotton, mustard and beans. Cobalt is required by symbiotic micro-organisms (e.g., rhizobia) for the fixation of elemental nitrogen through the formation of vitaminB12.
Cobalt forms a complex with nitrogen atoms of the porphyrin ring structure and provides a prosthetic group for association with nucleotides in vitamin B12 co-enzyme. This complex is called cobamide. Other cobalt functions include leghemoglobin metabolism and ribonucleotide reductase in Rhizobium, and activation of enolase, lecithinase and succinic kinase.
The concentration of cobalt in dry matter of plants ranges from 0.02 to 0.5 ppm. One ppb of cobalt in nutrient solution was found adequate for nitrogen fixation in alfalfa. The water content and catalase activity in leaves increased and the concentration of the cell sap decreased with cobalt application.
Cobalt content in soil is low and variable. In India, for instance, it ranges from 4 to 80ppm. The humus content of the soil influences the availability of cobalt in it. The nature of clay affects the absorption of cobalt from solutions, in the order muscovite > hematite > bentonite = kaolin. An increase in the pH of the soil decreases the availability of cobalt. Cobalt deficiency is more pronounced in coarse sandy soils and under high rainfall conditions. To overcome deficiency, cobalt fertilization with 100to 200g/ha as cobaltous sulphate (CoSO,) is recommended.
Industrial uses
Cobalt (symbol Co) is a lustrous, silvery-bluemetallic chemical element, resembling nickelbut with a bluish tinge instead of the yellow ofnickel. It is rarer and costlier than nickel andits price has varied widely in recent years.Although allied to nickel, it has distinctive differences.It is more active chemically thannickel. It is dissolved by dilute H2SO4, HNO3,or HCl acids, and is attacked slowly by alkalis.The oxidation rate of pure cobalt is 25 timesthat of nickel. Its power of whitening copperalloys is inferior to that of nickel, but smallamounts in Ni–Cu alloys will neutralize theyellowish tinge of the nickel and make themwhiter. The metal is diamagnetic like nickel, buthas three times the maximum permeability.Like tungsten, it imparts red-hardness to toolsteels. It also hardens alloys to a greater extentthan nickel, especially in the presence of carbon,and can form more chemical compoundsin alloys than nickel.
Its chemical properties resemble, in part,those of both nickel and iron. Cobalt is themetal with the highest Curie temperature(1121°C) and the lowest allotropic transformationtemperature (399°C). Below 421°C, cobaltis close-packed hexagonal; above, it is facecenteredcubic.
Biological Activity
Cobalt is a vital trace element in animal nutrition. Ruminants grazing upon cobaltdeficient pastures exhibit retarded growth, loss of appetite and anaemia ; rapid recovery from these symptoms occurs upon feeding the animals with a cobalt-supplemented diet. Cobalt salts are not therefore considered to be particularly toxic to animals, but to man they can in sufficiently large doses irritate the gastro-intestinal tract and cause nausea, vomiting and diarrhoea. Small amounts of cobalt, however, are invaluable in the treatment of pernicious anaemia. The discovery in 1926 of the antipernicious anaemia factor in liver led to the discovery in 1948 of vitamin B12, which was very soon after shown to contain cobalt.
Carcinogenicity
In mammalian cells in vitro cobalt compounds
have caused DNA strand breaks, sister
chromatid exchanges, and aneuploidy, but
not chromosomal aberrations.Cobalt salts
are generally nonmutagenic in prokaryotic
assays.
Environmental Fate
Cobalt most often depresses the activity of enzymes, including
catalase, amino levulinic acid synthetase, and P-450, enzymes
involved in cellular respiration. The Krebs citric acid cycle can
be blocked by cobalt resulting in the inhibition of cellular
energy production. Cobalt can replace zinc in a number of zincrequired
enzymes such as alcohol dehydrogenase. Cobalt can
also enhance the kinetics of some enzymes, such as heme
oxidase in the liver. Cobalt interferes with and depresses iodine
metabolism, resulting in reduced thyroid activity. Reduced
thyroid activity can lead to goiter.
Toxicity evaluation
The sources of cobalt in the environment are both natural and
synthetic (anthropogenic). Natural sources include soil,
seawater spray, volcanic eruptions, and forest fires. Anthropogenic
sources include combustion of fossil fuels, metal smelting,
sewage sludge, and processing of cobalt alloys. Cobalt is
found in the atmosphere in particulate form and returns to the
Earth’s surface through dry deposition and with rain or snow.
Once in surface water, cobalt generally moves into sediment.
Cobalt does not appear to biomagnify significantly in the
aquatic food chain. The cobalt that does accumulate in fish is
largely found in the nonedible parts of the fish. Seventy-nine
percent of the cobalt is transported by rivers globally and
precipitates in estuaries.
Under normal environmental conditions, cobalt is expected
to bind strongly to soil; thus, migration through soil is very
limited. Cobalt in soil can be taken up by plant roots and root vegetables, but does not translocate to the aboveground parts
of plants.
Incompatibilities
Cobalt metal dust/powder may spontaneously ignite on contact with air, when finely divided.Reacts with acids, strong oxidizers, ammonium nitrate,causing fire and explosion hazard. Can promote decomposition of various organic substances. Cobaltic oxide reactswith reducing agents; and violently with hydrogenperoxide
