Metallic mercury
Metallic mercury (liquid mercury, quicksilver,
hydrargyrum (hence Hg), elemental mercury), is a
silver white metal which melts at −38.7°C. Mercury
is best known as a liquid metal, having a vapour
pressure (a measure of the amount of vapour ‘given
off’) of 0.002 mm Hg at 25°C. This approximately
doubles for every 10°C increase in temperature, so
that heating metallic mercury greatly increases the
associated risks, as inhalation is the usual route of
toxicity. Inhaled mercury vapour accumulates in the
body, and in particular the central nervous system,
which is the site of its major toxic actions. Orally
ingested elemental mercury rarely causes acute toxic
effects, as gastro-intestinal absorption is low—less
than 0.01% of the dose.3 For practical purposes,
ingestion of oral elemental mercury as a single dose
poses a negligible risk of severe toxicity. The oral
LD10 is reported to be 1429 mg/kg (in man), or
approximately 100 g for a 70 kg adult. Percutaneous
absorption is also low (approximately 2% of the rate
of uptake by the lung