Mercury, also called quicksilver because it looks like silver and flows quickly, is the only metal that is liquid at an ordinary temperature. Small drops of pure mercury are sometimes found, but it is usually made from an ore, called cinnabar (mercuric sulphide), made up of mercury and sulphur. The metal is easily obtained by roasting the ore and vaporizing the mercury which is condensed and purified. The reaction is:

HgS

+

O2

=

Hg

+

SO2

Mercuric Sulphide

Oxygen

Mercury

Sulphur Dioxide

The sulphur burns to sulphur dioxide and the mercury passes off as a vapor. The vapor is conducted through tubes into a vessel containing water, where it is condensed into liquid mercury.

Pure mercury is very heavy, as bright as silver, and is not tarnished by air at an ordinary temperature. When heated it takes up oxygen from the air and is turned into a red powder (mercuric oxide). By continuing to heat the mercuric oxide, the oxygen can be driven off and the mercury turned back into a fluid state. Mercury becomes a solid only at a great degree of cold (39° to 40° F. below zero).