Bi - Bismuth
|Chemical Element||Bismuth||Melting Point °C||272|
|Chemical Symbol||Bi||Boiling Point °C||1560|
|Atomic Number||83||Density g/cm3||9.7|
Bismuth is a heavy, silvery-white metal with a faint pink or yellow tinge and is a member of Group 15 of the Periodic Table; it is the 70th most abundant element within the Earth’s crust. Bismuth is fairly resistant to corrosion, and is stable to both oxygen and water. As a metal it is too brittle to be used, and is the least metal-like of all the metals, having one of the lowest thermal conductivities and the highest electrical resistivity. When heated in air, it burns with a blue flame to produce yellow clouds of its oxide. In certain circumstances, bismuth can also behave as semiconductor, and bismuth telluride is just such a material used in infrared detectors.
Bismuth has been known since the early 15th century, but was often confused with tin and lead. It was discovered by an unknown alchemist around 1400 AD and began to be used for items such as making caskets. For three centuries, it was confused with lead, although a few scientists argued that it was clearly not lead, but it was not until 1753 that Claude-Francois Geoffrey finally proved that it was in fact its own element. The name bismuth is derived from the German ‘weisse masse’ which means, ‘white mass’.
The main mining areas for bismuth are Bolivia, Peru, Japan, Mexico, Canada and Australia. There are two bismuth minerals mined: native bismuth and bismuthinite, however it is also recovered from lead (Pb) and copper (Cu) smelters, where it is produced as a by-product. Bismuth is unusual in that it occurs naturally in its metal form, but it is also found as beautifully coloured crystals in sulphide ores of nickel (Ni), cobalt (Co), Silver (Ag) and Tin (Sn).
The world production is 3000 mt per year, while the reserves statistics are based on lead production and resources.
Due to bismuth’s properties, it has a variety of applications, including giving a lower melting point when alloyed with tin or lead. Due to this, it is often used for electric fuses and Wood’s metal (an alloy of bismuth and 12% cadmium (Cd)) which melts at 70°C used in automatic fire sprinkler systems.
As it is so brittle, it cannot be used as a metal outright and therefore needs to be alloyed with other elements, for example, zinc-bismuth alloys are used to achieve thinner and more uniform galvanisation. Other applications are as follows:
- it is used as a catalyst in manufacturing acrylonitrite for making synthetic fibres and rubbers
- in the manufacture of ceramic glazes, crystal ware, pigments
- an addition to free machining steels, malleable iron castings and brass
- as a non-toxic replacement to lead
- in the foundry industry (to enhance metallurgical quality)
- in pharmaceuticals.
And finally, bismuth-oxycholride is used to provide the luminescent, pearl quality in lipsticks and nail varnishes.
Today, research into new applications of bismuth is ongoing. It may be possible that liquid lead and bismuth coolants could be used for nuclear reactors, as well as producing bismuth-containing metal polymer bullets. Bismuth can be substituted by many other elements in its current applications, but it also substitutes lead in many. It is usually supplied in 10-14 kg ingots, with a chemistry of 99.99% required for solders and 99.97% regarded as pharmaceutical grade.
- Emsley, John. Nature’s Building Blocks, An A-Z Guide to the Elements, New Edition, Oxford University Press, 2011
- Gray, Theodore. The Elements, A Visual Exploration of Every Known Atom in the Universe, Black Dog & Leventhal Publishers, Inc, NY, 2009
- Stwertka, Albert. A Guide to the Elements, 3rd Edition, Oxford University Press, 2012