Gallium: the essentialsBrief description: it is the only metal, except for mercury, caesium, and rubidium, which can be liquid near room temperatures; this makes possible its use in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapour pressure even at high temperatures. Ultra-pure gallium has a beautiful, silvery appearance, and the solid metal exhibits a conchoidal fracture similar to glass. The metal expands on solidifying; therefore, it should not be stored in glass or metal containers, as they may break as the metal solidifies.
High-purity gallium is attacked only slowly by mineral acids. Gallium arsenide is capable of converting electricity directly into coherent light and gallium arsenide is a key component of LEDs (light emitting diodes). In the 1990s gallium nitride (GaN) was discovered to emit blue light in light-emitting diodes (LEDs). As red and green LEDs were already known, this meant that red green, and blue LEDS could be used in full-colour LED displays while white LEDs and blue laser devices became possible as well.
IsolationIsolation: gallium is normally a byproduct of the manufacture of aluminium. The purification of bauxite by the Bayer process results in concentration of gallium in the alkaline solutions from an aluminium:gallum ratio from 5000 to 300. Electrolysis using a mercury electrode gives a further concentration and further electrolysis using a stainless steel cathode of the resulting sodium gallate affords liquid gallium metal. Very pure gallium requires a number of further processes ending with zone refining to make very pure gallium metal. WebElements ShopWebElements now has an online shop at which you can buy periodic table posters, mugs, T-shirts, games, molecular models, and more. |
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