Historical
Facts and Elements Uses:
| Bismuth, «BIHZ muhth,» is a brittle, white metal with a
pink tint. It 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
is 83, and its atomic weight is 208.980. 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. |
|
