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DESIGNATIONS
CAS No.: 7440-48-4
Registry name: Cobalt
Chemical name: Cobalt
Synonyms, Trade names: Cobalt
Chemical name (German): Cobalt
Chemical name (French): Cobalt
Appearance: steel-grey, shiny, ferromagnetic metal
BASIC CHEMICAL AND PHYSICAL DATA
Chemical symbol: Co
Rel. atomic mass: 58.93 g
Density: 8.85 g/cm3 at 25°C
Boiling point: 2800°C +/- 50°C
Melting point: 1495°C
Vapour pressure: <10-5 Pa at 1250°C, >105 Pa at 3200°C
Solvolysis/solubility: readily soluble in diluted, oxidising acids
ORIGIN AND USE
Usage:
Dyeing of glass, ceramics and enamel by Co compounds. Production
of temperature-resistant, abrasion-proof and non-corroding alloys
(stellite). The synthetic radioactive isotope 60Co is
used in nuclear engineering and nuclear medicine (treatment of
tumours) as well as in other countries to preserve foodstuffs. Co
is used in the chemical industry in homogeneous and heterogeneous
catalysis to synthesise fuels (Fischer-Tropsch method) as well as
alcohols and aldehydes (hydroformylation). A further use is found
in the cemented carbides.
Origin/derivation:
Co makes up 0.0023% of the Earth's crust and is found together
with Cu, Ni and Fe ores. In most cobalt-containing ores, arsenic
is present, too. Co is manufactured by the partial roasting of
sulphide ores in the presence of fluxing agents. The resulting
raw material contains Cu, Ni and Co sulphides and arsenides at
higher concentrations. Further processing then involves heating
the raw material in the presence of NaCl.
Production figures:
In 1980: 32,700 t (worldwide) [ULLMANN, 1986]
Toxicity
| Mammals: | ||
| Rat | LD50 1750 mg/kg, (Co oxide) | acc. Ullmann, 1986 |
| Rat | LD50 821 mg/kg, (Co acetate) | acc. Ullmann, 1986 |
| Rat | LD50 766 mg/kg, (Co chloride) | acc. Ullmann, 1986 |
| Rat | LD50 691 mg/kg, (Co nitrate) | acc. Ullmann, 1986 |
| Rat | LD50 630 mg/kg, (Co carbonate) | acc. Ullmann, 1986 |
| Rat | LDLo 1500 mg/kg, oral | acc. UBA, 1986 |
| Rat | LDLo 100 mg/kg, intravenous | acc. UBA, 1986 |
| Rabbit | LDLo 20 mg/kg, oral | acc. UBA, 1986 |
| Rabbit | LDLo 100 mg/kg, intravenous | acc. UBA, 1986 |
| Aquatic organisms: | ||
| Daphnia | 1-9 mg/l = critical level, (Co chloride) | acc. LAU-BW, 1989 |
Characteristic effects:
Humans/mammals: Overdoses reduce the activity of the thyroid gland and can cause the formation of goitres. The number of erythrocytes in the blood increases (polycythemia), the blood vessels are temporally enlarged and blood coagulation is impaired. The nervous system is also frequently affected. Heart damage and pulmonary fibrosis (chron.) may occur. The most important aspect in toxicological terms is the inhalation of Co dust (proven carcinogenic effect; ROTH, 1989) and the hazard of sensitisation (ROTH, 1989). In addition, there is corrosion of the throat and the gastrointestinal tract if cobalt dusts have been inhaled. Poisoning causes disfunctions of the liver and kidneys.
Plants: A surplus of Co results in an Fe and Cu deficit (toxic effect = displacement effect). There is an increase in the number of chlorotic leaves which become necrotic and then die off.
ENVIRONMENTAL BEHAVIOUR
Air:
Cobalt is stable at normal temperatures in air. When heated, it
oxidises and burns at white heat to form Co3O4.
Soil:
The average Co content is 8 mg/kg. The solubility depends on
the pH. There is more elution in acid soils. Cobalt is bonded
above all to Mn and Fe oxides with the result that only small
quantities are available and thus mobile.
Degradation, decomposition products, half-life:
Renal discharge of inhaled cobalt: majority with a half-life
of 10 days, remainder with half-life of 90 days (MERIAN, 1984).
Food chain:
The absorption of cobalt in drinking water is insignificant.
Generally, the atmosphere is likewise only contaminated by traces
of cobalt. Humans absorb approx. 140 - 580 m
g of cobalt per day. Between 20% and 95% are resorbed. However,
most of the Co absorbed does not take the form of the necessary
vitamin B12, but is encountered rather as inorganic Co
bonded to foodstuff constituents. The absorption of inorganic Co
is linked to that of iron.
ENVIRONMENTAL STANDARDS
| Medium/ acceptor | Sector | Country/ organ. | Status | Value | Cat. | Remarks | Source |
| Water: | Surface | D | G |
0.05 mg/l | 1) For A + B | acc. LAU-BW, 1989 | |
| Groundw | D | (G) |
50 µg/l | Investigation | acc. LAU-BW, 1989 | ||
| Groundw | D | (G) |
200 µg/l | Rehabilitation | acc. LAU-BW, 1989 | ||
| Groundw | NL | G |
20 mg/l | Reference | acc. TERRA TECH, 6/94 | ||
| Groundw | NL | L |
100 mg/l | Intervention | acc. TERRA TECH, 6/94 | ||
| Waste water | CH | (L) |
0.05 mg/l | acc. LAU-BW, 1989 | |||
| Waste water | CH | (L) |
0.50 mg/l | Direct/indirect introduction | acc. LAU-BW, 1989 | ||
| Irrigation | D | G |
0.20 mg/l | Field cultivation | acc. LAU-BW, 1989 | ||
| Irrigation | D | G |
0.20 mg/l | Cultivation under glass | acc. LAU-BW, 1989 | ||
| Irrigation | USA | (L) |
0.20 mg/l | acc. LAU-BW, 1989 | |||
| Irrigation | USA | (L) |
10 mg/l | 2) | acc. LAU-BW, 1989 | ||
| Soil: | CH | G |
25 mg/kg | acc. LAU-BW, 1989 | |||
| D | (G) |
50 mg/kg | Investigation | acc. LAU-BW, 1989 | |||
| D | G |
300 mg/kg | Rehabilitation | acc. LAU-BW, 1989 | |||
| D | G |
800 mg/kg | acc. HOCK, 1988 | ||||
| NL | G |
20 mg/kg | Reference | acc. TERRA TECH, 6/94 | |||
| NL | L |
240 mg/kg | Intervention | acc. TERRA TECH, 6/94 | |||
| USA | G |
8000 mg/kg | TTLC | acc. DVGW, 1988 | |||
| USA | G |
80 mg/kg | STLC | acc. DVGW, 1988 | |||
| Sewage sludge | CH | L |
100 mg/kg | acc. LAU-BW, 1989 | |||
| Air: | Emiss. | D | L |
1 mg/m3 | mass flow > 5 g/h3) | acc. TA Luft, 1986 | |
| Workp | AUS | L |
0.1 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | B | L |
0.01 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | BG | L |
0.5 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | CH | L |
0.1 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | CS | L |
0.1 mg/m3 | Mean value | acc. MERIAN, 1984 | ||
| Workp | CS | L |
0.3 mg/m3 | Short-time value | acc. MERIAN, 1984 | ||
| Workp | D | L |
0.5 mg/m3 | TRK | use of powders | acc. LAU-BW, 1994 | |
| Workp | D | L |
0.1 mg/m3 | TRK | all other uses | DFG, 1994 | |
| Workp | DDR | L |
0.1 mg/m3 | Mean value | acc. MERIAN, 1984 | ||
| Workp | DDR | L |
0.1 mg/m3 | Short-time value | acc. MERIAN, 1984 | ||
| Workp | SF | L |
0.1 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | I | L |
0.1 mg/m3 | C, S | acc. MERIAN, 1984 | ||
| Workp | NL | L |
0.1 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | PL | L |
0.5 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | RO | L |
0.2 mg/m3 | Mean value | acc. MERIAN, 1984 | ||
| Workp | RO | L |
0.2 mg/m3 | Short-time value | acc. MERIAN, 1984 | ||
| Workp | S | L |
0.1 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | SU | L |
0.5 mg/m3 | acc. MERIAN, 1984 | |||
| Workp | USA | (L) |
0.1 mg/m3 | TWA | Emission class 3 | acc. LAU-BW, 1989 | |
| Workp | YU | L |
0.1 mg/m3 |
Notes:
1) For drinking water treatment in each case: A = impact limits up to which drinking water can be produced solely by natural methods; B = impact limits up to which drinking water can be produced with the aid of currently tried-and-tested chemophysical methods
2) Only suitable for short-term irrigation on certain soils.
3) Dustlike/aerosolic Co and its compounds in respirable forms, stated as Co
Comparison/reference values
| Medium/origin | Country | Value | Source |
| Water: | |||
| Lake Constance | D | < 0.2 µg/l | acc. DVGW, 1988 |
| Rhine (Mainz): | D | 6-12 µg/l | acc. DVGW, 1988 |
| Ruhr (Duisburg): | D | < 1 µg/l | acc. DVGW, 1988 |
| Seawater | 0.1 µg/l | acc. DVGW, 1988 | |
| Sediment: | |||
| Lake Constance | D | 5.7-18.9 mg/kg | acc. DVGW, 1988 |
| Rhine (Wiesbaden): | D | 20 mg/kg | acc. DVGW, 1988 |
| Ruhr (Wetter): | D | 25 mg/kg | acc. DVGW, 1988 |
| Fly ash (coal) | USA | 5-73 mg/kg | acc. HOCK, 1988 |
| Plants | 0.3-0.5 mg/kg | acc. HOCK, 1988 | |
Assessment/comments
Cobalt is the central atom in vitamin B12 and is an important trace element. The hazards emanating from cobalt compounds are slight when compared to other heavy metals. From the toxicological point of view it is important to avoid the inhalation of cobalt dusts.