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Mercury

DESIGNATIONS

CAS No.: 7439-97-6
Registry name: Mercury
Chemical name: Mercury
Synonyms, Trade names:
Quicksilver
Chemical name (German):
Quecksilber
Chemical name (French):
Mercure
Appearance:
silvery white, shiny metal, liquid at room temperature

BASIC CHEMICAL AND PHYSICAL DATA

Chemical symbol: Hg
Rel. atomic mass: 200.59 g
Density: 13.55 g/cm3
Relative gas density: 6.93
Boiling point: 357.3C
Melting point: -38.9C
Vapour pressure: 163 x 10-3 Pa
Solvolysis/solubility: in water: 60 g/l at 20C, 250 g/l at 50C
Conversion factors: 1 ppm = 8.34 mg/m3

1 mg/m3 = 0.12 ppm

BASIC DATA OF SELECTED COMPOUNDS

CAS No: 7487-94-7 21908-53-2
Chemical name: Mercury(II) chloride Mercury(II) oxide
Synonyms, Trade names: Mercuric chloride, Calochlor Mercuric oxide
Chemical name (German): Quecksilber(II)chlorid Quecksilber(II)oxid
Chemical name (French): Chlorure de mercure (II) Oxyde de mercure (II)
Appearance: white crystalline powder yellow to red crystalline powder (colour depends on size of crystals)
Empirical formula: HgCl2 HgO
Relative molecular mass: 271,5 g 216.59 g
Density: 5.43 g/cm3 11.1 g/cm3
Boiling point: 303C  
Melting point: 280C above 400-450C decomposition

(liberation of toxic Hg vapours)

Vapour pressure: 560 kPa at 280C 0.0012 hPa
Solvolysis/solubility: in water: 74 g/l at 20C

550 g/l at 100C

soluble in most organic solvents (alcohol, ether, benzene)

virtually insoluble in water (0.05 mg/l) and ethanol

ORIGIN AND USE

Usage:
Mercury is used as a cathode in the electrolysis of alkali-metal chlorides, in the production of batteries and pesticides, in the medical sector (amalgams and disinfectants), in the electrical industry (bulbs and components) as well as in pressure gauges and temperature measurement. For toxicological reasons its use in ointments and disinfectants is no longer standard practice.

Origin/derivation:
The Earth's crust contains an average of approximately 0.02 ppm of this element on average. Cinnabar (HgS) is the most widespread mercury mineral.

Mercury is ubiquitous. On average, freshwater contains 0.1 m g/l, seawater 0.03 m g/l and air 0.005-0.06 ng/m3 of mercury. Both inorganic and organic mercury compounds are hazardous to the environment. The organic compounds being much more poisonous. Some 70-80% of the total environmental impact is caused by natural emissions such as volcanoes or by evaporation from the Earth's crust or the oceans. About 20-30% is due to anthropogenic sources such as the mercury processing and ore dressing industry or the combustion of fossil fuels. Although this contribution is relatively small, there is no reason to underestimate the danger of mercury at high concentrations.

Production figures:
Mining production of mercury in 1984

USSR 1,600 t USA 657 t
Spain 1,520 t Mexico 384 t
China 800 t Algeria 377 t
World 5,814 t    

(figures from ULLMANN, 1990)

Toxicity

Characteristic effects:

Humans/mammals: In comparison with the liquid metal, mercury dusts and vapours are very toxic. It is subject to almost complete resorption via the lungs. The initial symptoms of acute poisoning are a sweet, metallic taste in the mouth together with nausea and vomiting. This is followed by inflammation of the mucous membranes in the respiratory organs. Mercury is finally stored in the liver and kidneys and is only excreted in bursts. Mercury-induced occupational diseases are subject to mandatory reporting in Germany. Chronic poisoning causes malfunction of the central nervous system, the symptoms being apathy, unretentive memory, overexcitability and general trembling. Mercury poisoning can prove fatal.

Inorganic mercury compounds
Mercury salts corrode the skin and mucous membranes. They are usually absorbed orally or dermally because of their low volatility. The intake of salts causes inflammation of the throat, difficulty in swallowing, drowsiness, vomiting, stomach pains, blood-tinged diarrhoea, circulatory collapse and shock. There is also swelling of the salivary glands, loosening of teeth and inflammation of the liver and kidneys.

Organic mercury compounds
Organic mercury compounds (especially alkyl mercury) are generally much more toxic than the inorganic. Moreover, acute poisoning by organic compounds develops completely different symptoms. In particular, poisoning caused by short-chain alkyl derivatives such as methyl or ethyl mercury only becomes apparent after some time (with the exception of pathological trembling); weeks usually pass following absorption. Typical symptoms include a restricted field of vision, unclear pronunciation and handwriting, abnormal hypersensitivity, irritation of the skin, nose bleeds and depression. Exposure to organic compounds attacks the nervous system (best-known epidemic: Minamata disease, Japan).

Methyl mercury dissolves readily in fat and passes through the blood-brain barrier and the placenta. It has a mutagenic and teratogenic potential (as a substance with a proven foetus-damaging effect, methyl mercury is listed in pregnancy group A in Germany).

Whereas only 0.01% of the metallic and some 15% of the inorganically bonded mercury is resorbed following oral intake, the resorption of organic compounds is up to 95% (DVGW, 1985).

Plants: Mercury compounds inhibit cell growth and impair permeability.

ENVIRONMENTAL BEHAVIOUR

Water:
Mercury inhibits the metabolic activity of microorganisms and thus suppresses the self-purification capability of water at concentrations as low as 18 m g/l. Mercury is adsorbed on sediment and suspended matter.

Air:
Mercury is washed out more or less completely by precipitations.

Soil:
Mercury accumulates in soil, preferably in humous soils.

Degradation, decomposition products:
Mercury is degraded by microorganisms (biomethylation) or oxidised to form Hg2+. Methylation produces methyl mercury in a reaction which is promoted by high pH values. Dimethyl mercury, which is only formed chemically (chemical methylation), escapes into the atmosphere and decomposes to form elemental mercury. Above all, rain impacted by mercury(II) ions can lead to the formation of monomethyl mercury out of inorganic mercury. In addition to methylation, chelate complexes may form from mercury(II) ions. Methyl mercury is a powerful fish toxin.

Food chain:
The mercury content may increase in plankton and aquatic animals by up to 500 times the concentration in seawater (DVGW, 1985). There is considerable accumulation in the food chain on account of its accumulation in the liver and kidneys.

Combination effects:
The effect of mercury is enhanced by the simultaneous intake of copper, zinc or lead.

ENVIRONMENTAL STANDARDS

Medium/ acceptor Sector Country/ organ. Status Value Cat. Remarks Source
Water: Surface D

L

0.0005 mg/l   1) acc. DVGW, 1985
Surface D

L

0.001 mg/l   2) acc. DVGW, 1985
Surface EC

G

0.0005 mg/l   3) acc. DVGW, 1985
Surface EC

G

0.001 mg/l   4) acc. DVGW, 1985
Drinkw CDN   0.001 mg/l     acc. DVGW, 1985
Drinkw CH   0.003 mg/l   1980 acc. MERIAN, 1984
Drinkw D

L

0.001 mg/l     acc. DVGW, 1985
Drinkw EC

G

0.001 mg/l     acc. DVGW, 1985
Drinkw J   0.001 mg/l   1968 acc. MERIAN, 1984
Drinkw SU   0.005 mg/l   1970 acc. MERIAN, 1984
Drinkw USA

(L)

0.002 mg/l     acc. DVGW, 1985
Drinkw USA

(L)

0.0005 mg/l   In State of Illinois acc. WAITE, 1984
Drinkw WHO

G

0.001 mg/l     acc. LAU-BW, 1989
Groundw NL

G

0.2 g/l   Reference acc. BACHMANN, 1987
Groundw NL

L

2 g/l   Intervention acc. BACHMANN, 1987
Waste water CH

(L)

0.001 g/m3   For drinking water acc. LAU-BW, 1989
Waste water D

L

0.05 g/m3     acc. ROTH, 1989
Irrigation D   2 g/l   5) acc. DVGW, 1985
Trough D   4 g/l   Maximum value acc. DVGW, 1985
Soil: Sewage sl. D

L

2 mg/kg   6) KLOKE, 1988
Sewage sl. D

L

25 mg/kg   7) KLOKE, 1988
  CH

G

0.8 mg/kg   8) acc. BAfUB, 1987
  GB

G

1.5 mg/kg   Domestic gardens acc. SAUERBECK, 1986
  GB

G

1 mg/kg   Vegetable gardens acc. SAUERBECK, 1986
  GB

G

50 mg/kg   9) acc. SAUERBECK, 1986
  NL

G

0.3 mg/kg   Reference acc. TERRA TECH 6/94
  NL

L

10 mg/kg   Intervention acc. TERRA TECH 6/94
Air: eMISS. d

l

0.2 mg/m3   mass flow > 1 g/h13) acc. TA Luft, 1986
  DDR L 0.0003 mg/m3 MIK   acc. HORN, 1989
Workp AUS

(L)

0.05 mg/m3     acc. MERIAN, 1984
Workp B

(L)

0.05 mg/m3     acc. MERIAN, 1984
Workp BG

(L)

0.0003 mg/m3   10) acc. MERIAN, 1984
Workp BG

(L)

0.01 mg/m3     acc. MERIAN, 1984
Workp CS

(L)

0.0003 mg/m3   10) acc. MERIAN, 1984
Workp CS

(L)

0.05 mg/m3   Long-time value acc. MERIAN, 1984
Workp CS

(L)

0.15 mg/m3   Short-time value acc. MERIAN, 1984
Workp D

L

0.1 mg/m3 MAK Mercury DFG, 1994
Workp D

L

0.01 mg/m3 MAK organic mercury compounds DFG, 1994
Workp D

L

200 g/l BAT metallic and inorg. compounds, urine DFG, 1994
Workp D

L

50 g/l BAT metallic and inorg. comp., whole blood DFG, 1994
Workp D

L

100 g/l BAT metallic and organic comp., whole blood DFG, 1994
Workp DDR

(L)

0.005 mg/m3   Long-time value acc. HORN, 1989
Workp DDR

(L)

0.01 mg/m3   Short-time value acc. HORN, 1989
Workp H

(L)

0.02 mg/m3   Skin acc. MERIAN, 1984
Workp IL

(L)

0.001 mg/m3   11) acc. MERIAN, 1984
Workp J

(L)

0.05 mg/m3     acc. MERIAN, 1984
Workp NL

(L)

0.05 mg/m3     acc. MERIAN, 1984
Workp PL

(L)

0.01 mg/m3     acc. MERIAN, 1984
Workp RO

(L)

0.001 mg/m3   10) acc. MERIAN, 1984
Workp RO

(L)

0.05 mg/m3   Long time value, skin acc. MERIAN, 1984
Workp RO

(L)

0.15 mg/m3   Short time value, skin acc. MERIAN, 1984
Workp S

(L)

0.05 mg/m3   Skin acc. MERIAN, 1984
Workp SF

(L)

0.05 mg/m3     acc. MERIAN, 1984
Workp SU

(L)

0.01 mg/m3 PDK   acc. SORBE, 1985
Workp USA

(L)

0.01 mg/m3 TWA Alkyl compounds ACGIH, 1986
Workp USA

(L)

0.03 mg/m3 STEL Alkyl compounds ACGIH, 1986
Workp YU

(L)

0.0003 mg/m3   10) acc. MERIAN, 1984
Workp YU

(L)

0.1 mg/m3   Skin acc. MERIAN, 1984
Foodstuffs:   D

G

0.01 mg/kg   Milk, cheese acc. GROKLAUS, 1989
  D

G

0.03 mg/kg   12) acc. GROKLAUS, 1989
  D

G

0.1 mg/kg   Animal's liver, kidneys acc. GROKLAUS, 1989
  D

G

0.05 mg/kg   Meat, sausage products acc. GROKLAUS, 1989

Notes:
The use of mercury compounds in pesticides has likewise been banned in the Federal Republic of Germany since 1980; their use in cosmetics is restricted to a few exceptions and the maximum content for fish in line with the Mercury Order (1975) is 1 mg/kg.

1) Limit value for natural treatment
2) Limit value for chemical and physical treatment
3) Guideline for physical and refined chemical treatment
4) Mandatory value for physical and refined chemical treatment
5) Maximum value for field and under-glass cultivation
6) Tolerable overall content in air-dry soil (limit value according to the Sewage Sludge Order)
7) Limit value for heavy metals in sewage sludge (limit value according to the Sewage Sludge Order)
8) Pollutant content in air-dried mineral soil (total content, HNO3 extract)
9) Public parks or open spaces
10) Limit values for mercury forming part of suspended dust
11) Provisional limit value for Israel
12) Hen's egg, beef, veal, pork, minced meat, chicken
13) Hg and its compounds, stated as Hg

Comparison/reference values

Medium/origin Country Value Source
Water:
Lake Constance (1982) D 0.003 g/l acc. DVGW, 1985
Neckar (1982) D 0.1 g/l acc. DVGW, 1985
Rhine (Cologne, 1983) D 0.01-0.2 g/l acc. DVGW, 1985
Rhine (Duisburg, 1983) D 0.03-0.13 g/l acc. DVGW, 1985
Danube (Leipheim, 1976) D 0.03 g/l acc. DVGW, 1985
Weser (Bremen, 1979) D 0.025-3.8 g/l acc. DVGW, 1985
Seawater J 12.5 ng/l acc. RIPPEN, 1989
North Sea   1.9-15 ppt acc. RIPPEN, 1989
Air:
Southern hemisphere (Africa):   2.3 ng/m3 acc. RIPPEN, 1989
USA:   1.9-36 ng/m3 acc. RIPPEN, 1989
Sediment:
Rhine (Cologne): D 10 mg/kg (1975-77) acc. DVGW, 1985
Neckar (Heidelberg): D 0.7 mg/kg (1975-77) acc. DVGW, 1985
Danube (Leipheim): D 1.2 mg/kg (1975-77) acc. DVGW, 1985
Port of Hamburg: D 11.2 mg/kg (1977) acc. DVGW, 1985
Mammals/humans:
Blood (human), normal value:   5 - 10 ng/ml acc. RIPPEN, 1989
Urine (humans), normal value:   1.5-8 g/d acc. RIPPEN, 1989
Seals:   <100-200 mg/kg acc. RIPPEN, 1989
Foodstuffs:
Fruit, vegetables:   0.25-33 ppb acc. RIPPEN, 1989
Grain:   0.5-640 ppb acc. RIPPEN, 1989
Meat, liver, etc.:   0.5-1.430 ppb acc. RIPPEN, 1989
Fish, fish products:   0.5-2.740 ppb acc. RIPPEN, 1989

Assessment/comments

Solid mercury in the form of pure metal is not poisonous to humans and, therefore, not hazardous. However, the use of mercury alloys (amalgams) as dental fillings is under discussion. Although the release of mercury into saliva is relatively low there is a tendency towards substitution of amalgams with less toxic materials such as ceramics or plastics. Particular attention must be paid to mercury vapours as well as to water pollution. Risk assessment of mercury compounds depends on the properties of the individual substance. Mercury(II) chloride and methyl mercury are particularly significant in this sense.


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