Page 26 - Curriculum Visions Dynamic Book

Mercury
Mercury, or quicksilver, is a shiny liquid metal, thirteen and a half times as heavy as an equal volume of
water. It is so dense that even lead can float on
the surface of mercury. The name quicksilver, or
living silver, came about from the silvery globules that form and roll about when mercury is poured onto a surface.
Mercury is a rare metal,
yet it was one of the first
metals ever found. Its ore,
called cinnabar, is bright red and was
used by the Chinese for three thousand years as a colour for paint. Cinnabar is also found in ancient Egyptian tombs dating back nearly 4000 years
The ancient Greeks used mercury as
a medicine. In fact, mercury compounds can be used as disinfectants, but mercury itself is very toxic and can do far more harm than good! Mercury is poisonous because
it can “switch off ” enzymes in the body.
Mercury is a liquid between -39°C
(at which it solidifies) and 357°C (at which it boils). It has a high surface tension, which is why it forms globules rather
than spreading out over surfaces.
Alloys of mercury with another metal are called amalgams. Mercury makes liquid alloys with gold, silver, copper and lead.
Mercury gives off a toxic vapour when exposed to the air, even at temperatures well below its boiling point. This limits its uses in many applications. The main uses for mercury are as amalgams and in thermometers and barometers.
 Mercury’s strong surface tension keeps the liquid formed as small globules.
Cinnabar
Mercury makes 83 parts per billion of the world’s surface rocks, just a little more plentiful than gold. It is not thought of as a rare metal, however,
because it is found in naturally concentrated form. Its main ore is mercury sulphide (HgS), called cinnabar.
To refine the ore the rock is ground up and heated, causing mercury vapour to rise from the ore. The vapour is distilled.
Cinnabar is found in places where there has been volcanic activity, where it was probably precipitated from hot waters rising above a magma chamber. The main mine for cinnabar is
at Almaden, Spain. This mine has been worked since Roman times.
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