Bismuth Bi

Discovery

Bismuth was known to European miners and metalworkers from the late Middle Ages, but it was long confused with tin, lead or antimony. In fifteenth-century Germany bismuth alloys were even used for printing type.

In 1753 the French chemist Claude François Geoffroy showed clearly that bismuth is a distinct metal, and that date is usually given for its discovery. For a long time bismuth was regarded as the heaviest stable element. In 2003, however, French researchers detected an extremely slow alpha decay of bismuth-209, and the title passed to lead.

Origin of the name

The origin of the name is uncertain. A popular explanation traces it to the German weiße Masse, "white mass", but other derivations have been proposed. The Latinised form bisemutum was recorded by the sixteenth-century German mining scholar Georgius Agricola, who helped spread the name.

Main uses

• Medicines: bismuth subsalicylate is the active ingredient in over-the-counter remedies for diarrhoea and indigestion, and bismuth compounds are part of combination therapies for eradicating Helicobacter pylori, the bacterium behind many stomach ulcers.
• Low-melting alloys: bismuth alloys such as Wood's metal melt at low temperatures and are used in fire-sprinkler plugs and safety fuses.
• Lead replacement: thanks to its low toxicity it replaces lead in lead-free solder, fishing weights and shotgun pellets.
• Cosmetics and pigments: bismuth oxychloride gives a pearly sheen to cosmetics, and bismuth vanadate is a bright yellow pigment.

Isotopes

Natural bismuth is essentially all bismuth-209. Its half-life is about 2 × 10^19 years, more than a billion times the age of the universe, so for practical purposes it is stable. Artificial bismuth-213 (half-life about 46 minutes) is studied for targeted alpha therapy of cancer, and bombarding bismuth-209 with neutrons in a reactor is how polonium-210 is made.

In everyday life

When molten bismuth cools slowly, the edges of each crystal grow faster than the faces, producing hollow, stair-stepped "hopper" crystals; a thin oxide layer on the surface creates rainbow colours through light interference. The crystals sold in science shops are grown artificially this way. Bismuth is the most diamagnetic element, so a small piece can be levitated above a strong magnet, and like water it expands when it solidifies. Bismuth stomach medicines can temporarily turn the tongue or stools black, which is a harmless and common effect.