Page 34 - Curriculum Visions Dynamic Book

When electricity is passed through mercury vapour, it gives off a bluish glow, so it is used in street lighting and in fluorescent lamps. Mercury is alloyed with many metals to form amalgams. Amalgams are used in dental fillings.
Geology
It is occasionally found as a native liquid metal, but much more commonly as the red mineral cinnabar (mercury sulphide, HgS). Mercury is a rare element.
Biology
Mercury vapour is poisonous. It can be absorbed by breathing, through contact with the skin and by absorption in the digestive system. It is not easily removed from the system and builds up in the body. It is not safe to be in a room with free liquid mercury.
 Mercury’s strong surface tension keeps the liquid formed as small globules.
All mercury compounds are extremely toxic.Yet mercury is used to remove gold from its ores, which releases vapours that are toxic. Many gold miners in developing countries suffer from their effects.
Mercury affects the central nervous system. It used to be used in hat making, and its effect on hatters gave rise to the term ‘mad as a hatter’. Mercury poisoning can also come about from the improper disposal of mercury wastes from factories. One example, in the sea around Japan, led to many deaths.
Mercurous chloride Hg2Cl2 (as calomel) has been used as a medicine.
For more on mercury, see 6: Zinc, Cadmium, and Mercury in the Elements set.
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