Bismuth compounds are used in cosmetics, medicines, and in medical procedures. As the toxicity of lead has become more apparent in recent years, alloy uses for bismuth metal as a replacement for lead have become an increasing part of bismuth's commercial importance.
Bismuth is a brittle metal with a white, silver-pink hue, often occurring in its native form with an iridescent oxide tarnish showing many refractive colors from yellow to blue. When combusted with oxygen, bismuth burns with a blue flame and its oxide forms yellow fumes. Its toxicity is much lower than that of its neighbors in the periodic table such as lead, tin, tellurium, antimony, and polonium.
Although ununpentium is theoretically more diamagnetic, no other metal is verified to be more naturally diamagnetic than bismuth. (Superdiamagnetism is a different physical phenomenon.) Of any metal, it has the second lowest thermal conductivity (after mercury) and the highest Hall coefficient. It has a high electrical resistance. When deposited in sufficiently thin layers on a substrate, bismuth is a semiconductor, rather than a poor metal.
Elemental bismuth is one of very few substances of which the liquid phase is denser than its solid phase (water being the best-known example). Because bismuth expands on freezing, it was long an important component of low-melting typesetting alloys, which needed to expand to fill printing molds.
"Artificial bismuth" was commonly used in place of the actual metal. It was made by hammering tin into thin plates, and cementing them by a mixture of white tartar, saltpeter, and arsenic, stratified in a crucible over an open fire.
The most important ores of bismuth are bismuthinite and bismite. In 2005, China was the top producer of bismuth with at least 40% of the world share followed by Mexico and Peru, reports the British Geological Survey. Native bismuth is known from Australia, Bolivia, and China.
According to the USGS, world 2006 bismuth mine production was 5,700 tonnes, of which China produced 3,000 tonnes, Mexico 1,180 tonnes, Peru 950 tonnes, and the balance Canada, Kazakhstan and other nations. World 2006 bismuth refinery production was 12,000 tonnes, of which China produced 8,500 tonnes, Mexico 1,180 tonnes, Belgium 800 tonnes, Peru 600 tonnes, Japan 510 tonnes, and the balance Canada and other nations.
The difference between world bismuth mine production and refinery production reflects bismuth's status as a byproduct metal. Bismuth travels in crude lead bullion (which can contain up to 10% bismuth) through several stages of refining, until it is removed by the Kroll-Betterton process or the Betts process. The Kroll-Betterton process uses a pyrometallurgical separation from molten lead of calcium-magnesium-bismuth drosses containing associated metals (silver, gold, zinc, some lead, copper, tellurium, and arsenic), which are removed by various fluxes and treatments to give high-purity bismuth metal (over 99% Bi). The Betts process takes cast anodes of lead bullion and electrolyzes them in a lead fluosilicate-hydrofluosilicic acid electrolyte to yield a pure lead cathode and an anode slime containing bismuth. Bismuth will behave similarly with another of its major metals, copper. Thus world bismuth production from refineries is a more complete and reliable statistic.
According to the Bismuth Advocate News, the price for bismuth metal from year-end 2000 to September 2005 was stuck in a range from $2.60 to $4.15 per lb., but after this period the price started rising rapidly as global bismuth demand as a lead replacement and other uses grew rapidly. New mines in Canada and Vietnam may relieve the shortages, but prices are likely to remain above their previous level for the foreseeable future.
Though virtually unseen in nature, high-purity bismuth can form distinctive hopper crystals. These colorful laboratory creations are typically sold to collectors. Bismuth is relatively nontoxic and has a low melting point just above 271 °C, so crystals may be grown using a household stove, although the resulting crystals will tend to be lower quality than lab-grown crystals.
Some other current uses:
In the early 1990s, research began to evaluate bismuth as a nontoxic replacement for lead in various applications:
According to the USGS, U.S. bismuth consumption in 2006 totaled 2,050 tonnes, of which chemicals (including pharmaceuticals, pigments, and cosmetics) were 510 tonnes, bismuth alloys 591 tonnes, metallurgical additives 923 tonnes, and the balance other uses.
Fine bismuth powder can be pyrophoric.
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