Bismuth

Bismuth is a chemical element in the periodic table that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony. Of all the metals, it is the most naturally diamagnetic, and only mercury has less thermal conductivity. Lead-free bismuth compounds are used in cosmetics and in medical procedures.

1 Notable characteristics
2 Applications
3 Crystals
4 History
5 Occurrence
6 See also
7 References
8 External links

Notable characteristics

It is a brittle metal with a pinkish hue and an iridescent tarnish. Among the heavy metals, bismuth is unusual in that its toxicity is much lower than that of its neighbors in the periodic table such as lead, thallium and antimony. Traditionally, it has also been regarded as the element with the heaviest stable isotope, but this is now known to be untrue (see below). No other metal is more naturally diamagnetic (as opposed to superdiamagnetic) than bismuth. It occurs in its native form, and has a high electrical resistance. Of any metal, it has the second lowest thermal conductivity and the highest Hall effect. When combusted with oxygen, bismuth burns with a blue flame and its oxide forms yellow fumes.

Bismuth has long been thought to be unstable on theoretical grounds, but not until 2003 was this demonstrated when researchers at the Institut d'Astrophysique Spatiale in Orsay, France measured the alpha emission half-life of Bi-209 to be 1.9 × 10¹⁹ years, meaning that bismuth is very slightly radioactive, with a half-life over a billion times longer than the current estimated age of the universe. Due to this phenomenal half-life, bismuth can be treated as if it is stable and non-radioactive. Ordinary food containing typical amounts of Carbon-14 is many thousands of times more radioactive than bismuth, as are our own bodies. However, the radioactivity is of academic interest because bismuth is one of few elements whose radioactivity was suspected, and indeed theoretically predicted, before being detected in the lab.

Applications

Bismuth oxychloride is extensively used in cosmetics and bismuth subnitrate and subcarbonate are used in medicine. Bismuth subsalicylate (Pepto-Bismol®) is used as an antidiarrheal. Some other current uses are:

Strong permanent magnets can be made from the alloy bismanol (MnBi).
Many bismuth alloys have low melting points and are widely used for fire detection and suppression system safety devices.
Bismuth is used in producing malleable irons.
Bismuth is finding use as a catalyst for making acrylic fibers.
Also used as a thermocouple material (bismuth has the highest negativity known).
A carrier for U-235 or U-233 fuel in nuclear reactors.
Bismuth has also been used in solders. The fact that bismuth and many of its alloys expand slightly when they solidify make them ideal for this purpose.
Bismuth subnitrate is a component of glazes that produces an iridescent luster finish.
Bismuth is sometimes used in the production of shot and shotgun slugs. Its advantage over lead in this respect is that is non-toxic so is therefore legal in the UK for the shooting of wetland birds.

In the early 1990s, research began to evaluate bismuth as a nontoxic replacement for lead in various applications:

As noted above, bismuth has been used in solders; its low toxicity will be especially important for solders to be used in food processing equipment.
As an ingredient of ceramic glazes
As an ingredient in free-machining brasses for plumbing applications
As an ingredient in free-cutting steels for precision machining properties
As a catalyst for making acrylic fibres
As a carrier for uranium fuel in nuclear reactors
In low-melting alloys used in fire detection and extinguishing systems
As an ingredient in lubricating greases
As a dense material for fishing sinkers.

Crystals

Synthetic Bismuth crystal

Though virtually unseen in nature, high-purity bismuth can form into distinctive hopper crystals. These colorful laboratory creations are typically sold to hobbyists.

History

Bismuth (New Latin bisemutum from German Wismuth, perhaps from weiße Masse, "white mass") was confused in early times with tin and lead due to its resemblance to those elements. Claude Geoffroy le Jeune (Claude Geoffroy the younger) showed in 1753 that this metal is distinct from lead.

Artificial bismuth was commonly used in place of the actual mineral. It was made by reducing tin into thin plates, and cementing them by a mixture of white tartar, saltpeter, and arsenic, stratified in a crucible over an open fire. ^[2]

Occurrence

The most important ores of bismuth are bismuthinite and bismite. Canada, Bolivia, Japan, Mexico, and Peru are major producers. Bismuth produced in the United States is obtained as a by-product of copper, gold, silver, tin and especially lead ore processing. The average price for bismuth in 2000 was US$7.70 per kilogram.