Platinum is a lustrous silvery-white, malleable, ductile metal and
a member of group 10 of the periodic table of the elements. It has
the third highest density, behind osmium and iridium. Platinum is
unaffected by air and water, but will dissolve in hot aqua regia,
in hot concentrated phosphoric and sulphuric acids, and in molten
alkali. It is as resistant as gold to corrosion and tarnishing.
Indeed, platinum will not oxidize in air no matter how strongly it
is heated.
It has a coefficient of expansion almost equal to that of
soda-lime-silica glass, and is therefore used to make sealed
electrodes in glass systems. Hydrogen and oxygen gas mixtures
explode in the presence of platinum wire.
