Page 35 - Curriculum Visions Dynamic Book

High-quality mirrors
Specialised mirrors are needed for precision scientific work. For these, silver is vaporised
by heating it in a vacuum chamber. It is then condensed on to the glass as a thin even coating.
For a large-scale use of mirrors, such as in solar power stations, aluminium is often used as a substitute for silver. It is not quite such
a good reflector, but it is very much cheaper.
amalgam: a liquid alloy of mercury with another metal.
cell: a vessel containing two electrodes and an electrolyte.
electrolyte: a solution that conducts electricity.
 The metal-based fillings in grinding teeth are made with either silver or gold amalgams.
In silver-based amalgam the proportions
of metals by weight are: 52% mercury,
33% silver, 12.5% tin, 2% copper and 0.5% zinc.
As the amalgam sets, it expands slightly, locking itself into the tooth cavity.
Also...
If you have metal-based amalgam fillings and
you chew a piece of “silver” or other metal foil, it is possible to get a shooting sensation through the filled teeth. In effect you will be repeating one of the world’s earliest electrical experiments, where Luigi Galvani made frogs’ legs twitch by using the body fluids and two different metals to create
a battery (an electrical cell). In the case of the silver foil, the amalgam and the silver foil are two different metal electrodes, and your saliva is the electrolyte of the cell, so that a current will flow. This current may well cause a painful sensation in your tooth if the filled cavity is deep and the filling is close to the dental nerve.
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