Bismuth << BIHZ muhth >> is a brittle, white metal with a pink tint. Bismuth is an element that is is found free in nature and in such ores as bismuth glance and bismite. Bolivia has the largest deposits of the metal. However, bismuth is generally obtained as a by-product in refining lead, copper, tin, silver, and gold ores, especially in the United States.
More than half the world’s bismuth is used as a metal or in alloys. Bismuth is mixed with lead, tin, or iron to form fusible metals, which melt at low temperatures. In a steam boiler, for example, safety plugs made of these alloys will melt and let the steam escape before the pressure increases enough to burst the boiler. Similar plugs are used in automatic sprinkler systems. Heat from a fire melts the plugs and turns on the system. In electrical fuses, metal strips of these alloys melt when the electric current is too high.
Bismuth is also used in foundries and in nuclear reactors. Bismuth alloys give sharp impressions when they are used to make objects by casting in molds. Because bismuth does not absorb neutrons readily, melted bismuth is used to carry radioactive fuel to the core of certain nuclear reactors. It also helps cool the reactor.
Bismuth and its compounds have uses in medicine as well. For example, bismuth carbonate and bismuth subnitrate are prescribed for diarrhea, enteritis, gastric ulcers, and certain skin disorders. Bismuth compounds are also used in making cosmetics and certain drugs. But some medical experts warn against using certain substances containing bismuth because these substances have been found to cause toxic reactions.
The chemical symbol of bismuth is Bi. The element’s atomic number (number of protons in its nucleus) is 83. Its relative atomic mass is 208.98038. An element’s relative atomic mass equals its mass (amount of matter) divided by 1/12 of the mass of an atom of carbon 12, the most abundant form of carbon. Bismuth melts at 271.3 °C and boils at 1560 °C (plus or minus 5 °C). Its density is 9.747 grams per cubic centimeter at 20 °C. For information on the position of bismuth on the periodic table, see the article Periodic table .
