Bismuth
Bismuth is the fifth and last element in Group 15 of the periodic table. Elements in this group are often referred to as the nitrogen family. Bismuth's atomic number is 83, its atomic mass is 208.9804, and its chemical symbol is Bi.
Properties
Bismuth is a soft, silvery metal with a bright, shiny surface and a yellowish or pinkish tinge. The metal breaks easily and can not be fabricated at room temperature. Its melting point is 520°F (271°C) and its boiling point is 2,840°F (1,560°C). Its density is 9.78 grams per cubic centimeter.
A somewhat unusual and valuable property of bismuth is its tendency to expand as it cools. Most liquids contract as they cool, so bismuth is an exception to the general rule. This property leads to some important applications of the metal. For example, when used as an alloy in type metal, it expands to fill all the corners of a mold, forming clean, crisp letters, numbers, and symbols.
Chemically, bismuth is a relatively active metal that combines with oxygen at room temperature. The bismuth oxide (Bi2O3 thus formed is responsible for the yellowish or pinkish tinge of the metal's surface.
Occurrence and Extraction
Bismuth is a relatively rare element in the Earth's crust with an abundance estimated at about 0.2 parts per million. It is rarely found in its elemental state. Its compounds tend to be found with ores of other metals, such as lead, silver, gold, and cobalt. The most important ore of bismuth is bismuthinite, also known as bismuth glance (Bi2S3). The largest producers of bismuth in the world are Mexico, Peru, China, Belgium, and Japan. Bismuth is produced in the United States only as a byproduct of lead refining at a plant in Nebraska.
Discovery and Naming
Bismuth and its compounds have been known for hundreds of years. During the fifteenth century, some of the first printing presses used type made of bismuth alloys. Scholars had a great deal of trouble distinguishing arsenic, antimony, and bismuth from each other. In fact, the first clear description of bismuth as an element was probably a book written by the French scholar Claude-Françoise Geoffrey in 1753.
The origin of bismuth's name is also uncertain. Historians of science believe that the name may have come from two German words, weisse masse, meaning "white mass." This phrase describes the appearance of the element in nature. Later the name was shortened to wismuth, and then to bisemutum before bismuth came into common use.
Uses
The primary use of bismuth metal is in the manufacture of alloys. A number of these alloys have low melting points, some as low as 158°F (70°C). Since this temperature is less than the boiling point of water, such alloys can be used in fire sprinkler systems, fuel tank safety plugs, solder, and other applications.
Recently there has been an increased interest in the use of bismuth as a substitute for lead in alloys. Bismuth adds many of the same properties to an alloy as does lead, but it is much less toxic. As an example, an alloy containing 97% bismuth and 3% tin is popular as shot used in waterfowl hunting.
Two-thirds of the bismuth produced in the United States is made into drugs, pharmaceuticals, and other chemicals. The most widely used compound is bismuth subsalicylate [Bi(C7H5O3)3], the active ingredient in many over-the-counter stomach remedies. Other compounds of bismuth are used for other medical purposes, such as the treatment of burns, stomach ulcers, and intestinal disorders. They also find wide application in cosmetics. Bismuth oxychloride (BiOCl), for example, is a lustrous white powder that is used in making face powder.
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