Mercury & compounds

Description

Mercury is used in its pure form in thermometers and barometers. Many batteries contain mercury. It is used in floodlights, streetlights, and other outdoor or powerful lights. It is also used as a catalyst in the chemical manufacturing industry. It is used to conduct electricity (i.e. thermostats). Mercury is used in dental amalgams. It is also used in the mining industry to extract gold and silver ores. Mercuric chloride is used in the manufacture of disinfectants, other chemicals, and as a catalyst. Mercuric chloride is used in photography and embalming. Bacteria in the water and the soil primarily produce methyl mercury.

Substance details

Substance name: Mercury & compounds

CASR number: 
Mercury: 7439-97-6
Mercury bichloride: 7487-94-7
Methyl Mercury: 22967-92-6

Molecular formula: 
Mercury: Hg
Mercury bichloride: HgCl2
Methyl Mercury: CH3Hg+

Synonyms: Mercury: Quick Silver, Liquid silver, hydragyrum.

Mercury bichloride: Mercuric bichloride, mercuric chloride, Bichloride of Mercury, Corrosive Sublimate, Mercury perchloride, Mercury (II) Chloride, Mercury chloride, perchloride of mercury, sublimate

Physical properties

Mercury, a naturally occurring element, is an odourless, very heavy, silver white, liquid metal. Mercuric chloride is an odourless, white powder or crystal. Both mercury and mercuric chloride are slightly volatile at ordinary temperatures.

Mercury:

Melting Point: -39°C

Boiling Point: 357°C

Specific Gravity: 13.6

Vapour Pressure: 0.0012 (mm Hg/21°C)

Mercuric chloride:

Melting Point: 277°C

Boiling Point: 320°C

Specific Gravity: 5.4

Vapour Pressure: 1.3 (mm Hg/21°C)

Chemical properties

Pure mercury is stable and does not tarnish at ordinary temperatures. It will form alloys with most metals. It is not soluble in water or most other liquids, but will dissolve in lipids (fats and oils). It is an excellent conductor of electricity. Mercuric chloride and methyl mercury are both soluble in most organic solvents. Mercuric chloride is soluble in water, methyl mercury is not.

Further information

The National Pollutant Inventory (NPI) holds data for all sources of mercury and compounds emissions in Australia.

Description

The nervous system is very sensitive to all forms of mercury. Exposure to high levels of any types of mercury can permanently damage the brain, kidneys, and developing foetus. Effects on brain functions may result in irritability, shyness, tremors, changes in vision or hearing and memory problems. High exposures of mercury vapour may cause chest pain, shortness of breath, and a build up of fluids in the lungs (pulmonary oedema) that can be fatal. Methyl mercury and mercury metal vapours are especially harmful, because more mercury reaches the brain. Long term exposures may cloud the eye. Contact with mercuric chloride can cause burns to the skin and permanent damage to the eyes. Mercury also accumulates in the body.

Entering the body

Mercury and mercury containing products will enter the body if we breathe in contaminated air, drink contaminated water, eat contaminated food, or have our skin come into contact with it. Mercury may be absorbed through the skin. Mercury released into the environment is converted into methyl mercury by bacteria. The methyl mercury will then build up in the tissues of fish and shellfish. Humans (and other animals) may also be poisoned by eating these fish or shellfish.

Exposure

Mercury can be absorbed through the skin. Workers in the industries that use or produce mercury and its compounds (mercury mines and refineries, chemical manufacturing, dental/health fields, metal smelters) are at risk of exposure. Workers in fossil fuel power plants and in cement manufacturing may be exposed to mercury compounds if they are exposed to gaseous process emissions. Consumers can be exposed to mercury and its compounds by exposure to air from production and processing facilities using mercury and its compounds, by eating fish or shellfish contaminated with methyl mercury. People can also be exposed to mercury from dental work and medical treatments.

Workplace exposure standards

Safe Work Australia sets the workplace exposure standard for mercury through the workplace exposure standards for airborne contaminants:

  • Maximum eight hour time weighted average (TWA): 0.003 parts per million (0.025 mg/m3)

These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.

Drinking water guidelines

The Australian Drinking Water Guidelines include the following guidelines for acceptable water quality:

  • Maximum of 0.001 milligrams per litre of water for health purposes

Description

Both mercury and its compounds have high acute (short-term) and have high chronic (long-term) toxicity on aquatic life. Eating fish contaminated with mercury has caused poisoning in humans; birds and land animals exposed in the same manner could also be subject to the same effects. There is not sufficient data to determine the acute toxicity of mercury and its compounds on plants, birds or land animals. Mercury and its compounds are highly persistent in water and the environment and will bioaccumulate or concentrate in the tissues of fish. These concentrations will be considerably higher than the water from which the fish is taken.

Entering the environment

Mercury chloride will act as a particle, following wind patterns, and being deposited by rain. Elemental mercury may be a gas in the atmosphere. Emissions of mercury and or mercury compounds can produce elevated, but still low-level concentrations in the atmosphere around the source. Elemental mercury can evaporate from both soil and water into the atmosphere.

Where it ends up

When mercury enters the environment from emissions in the air, water or soil, it oxidises into other compounds of mercury. These other forms of mercury form methyl mercury, through either chemical or biological (bacteria) processes. Methyl mercury builds up in the tissues of fish and shellfish. In areas of mercury contamination, larger and older fish tend to have higher levels of mercury. Mercury emitted to the environment will remain for years.

Environmental guidelines

Australian Water Quality Guidelines for Fresh and Marine Waters: (ANZECC, 1992):
Maximum of 0.0001 mg/L (i.e. 0.0000001 g/L)

Industry sources

Fossil fuel power plants emit to air, precious metal mining operations may emit to water or land, metal smelters may emit to air, cement manufacture may emit to air. Municipal landfills, sewage, metal refining, and chemical manufacturing are also significant potential emitters of mercury to land and water.

Diffuse sources, and industry sources included in diffuse emissions data

Burning of fossil fuels (home heating oil, petrol) emits to air, disposal of batteries, thermometers and other mercury containing products may emit to land, and photographic processing facilities may emit mercury to water.

Natural sources

Mercury is a naturally occurring element that is found in rocks and ores. Mercury is released into the atmosphere by evaporating from soils, from volcanic activity, and from burning of fossil fuels (coal, oil, petrol, asphalt, etc.).

Transport sources

The combustion of petrol releases small amounts of mercury to air.

Consumer products

Batteries, thermometers, barometers, thermostats, and mercury lights are some of the consumer products that contain mercury. Photographic toners contain mercuric chloride.

Sources used in preparing this information

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