Mercury
Mercury (quicksilver), chemical formula Hg, is a metal that is liquid at room temperatures. It is mostly found in cinnabar ore (HgS), and is generally only found free in the air near cinnabar mines. Mercury should be handled with care, particularly at warmer temperatures, and should not be touched as it can be absorbed through the skin. It is easily alloyed with other metals such as gold, silver, and tin to form amalgams. This makes it useful for recovering gold from ores.
Mercury forms a variety of compounds:
- methyl mercury - lethal pollutant, often from industrial waste, settles on river and lake bottoms
- mercuric sulphide HgS - vermilion, a paint pigment
- mercuric chloride HgCl2 - poisonous, volatile
- mercury fulminate Hg(ONC)2 - used in detonators, can be replaced by lead azide PbN3
- mercurous chloride Hg2Cl2 - used in old medicines
The element mercury can cause allergic reactions and can permanently damage the brain and kidneys. Swallowing even small amounts of mercury compounds, particularly organic compounds such as methyl mercury, can cause major neurological damage and death.
Very small amounts can have severe effects on the brain and nervous system development of foetuses, infants and children. These small amounts can be passed on by the mother who may have eaten contaminated food. Children's memory, attention, language and other skills may be impaired.