Page 36 - Curriculum Visions Dynamic Book

Amalgams
An amalgam is a mixture, or liquid alloy, of metals with mercury. Amalgams are extremely useful. As early as
the 16th century the Venetians used an amalgam of
one part tin and two parts mercury as a reflective backing (called “silvering”) to make the world’s first glass mirrors. (Mirrors are now made with silver and aluminium.)
Amalgams have been used for extracting precious metals such as gold and silver from their ores. They are used widely in industry (see the mercury cathode cell process on page 33), and in dentistry, where the metal fillings are
amalgams with silver or gold.
Mercury “eats” holes in thin sheet metal
When mercury is dropped on to the surface of a thin sheet of shiny aluminium, the two elements form an amalgam. Because the sheet is
thin, all the aluminium mixes with the mercury
at the places where the mercury droplets settle. The result is a pattern of holes where the aluminium has simply become part of the amalgam, which then falls away.
Because it is liquid, mercury cannot develop a coating of unreactive oxide. Thus it is particularly reactive with other metals.
 Mercury forms an amalgam with aluminium, corroding holes in this aluminium foil sample.
36
36