Bismuth

Bismuth: A Help In Many Ways |

Written by Tom Vulcan    |
March 02, 2009 2:12 PM EST |
| |
 Have you even wondered what the "Bis" is in Pepto-Bismol? Yes, you're right; it's bismuth!And not just in Pepto-Bismol: bismuth, in a number of different chemical compounds, is to be found in a variety of both cosmetics and pharmaceuticals. For example, internally, both bismuth subnitrateand subcarbonate are used to help with adverse stomach and intestinal conditions. And medicines containing bismuth have been used successfully to treat both duodenal and peptic ulcers. Externally, bibrocathol - another compound containing bismuth - is used to treat eye infections; for example, blepharitis, which causes inflammation of the eyelids.In cosmetics, bismuth oxychloride (or Bismuth White)is commonly used in lipsticks and eye shadows, not only to give the makeup its sheen, or pearly look, but also to help it actually adhere to the skin. Bismuth oxide is also used as a yellow pigment in cosmetics (and paints).Of all the bismuth consumed in the U.S. last year, according to the United States Geographical Survey (USGS), some 31% was used in pharmaceuticals and various otherchemicals. U.S. Bismuth Consumption - 2008* For castings and galvanizingSource: USGS Why Bismuth?There are a number of reasons, most associated with some of bismuth's extraordinary characteristics.In its pure form, bismuth is a heavy, brittle, white metal with a hint of pink. For much of its early history, it was mistaken for either of, or both, tin and lead, until 1753, when Claude François Geoffroy, aFrench chemist, demonstrated it was a separate element.However, in sharp contrast to lead, bismuth is, in fact, the least toxic of all the heavy metals. Hence its current use in cosmetics (where once lead was sometimes used) and its increasing use as a substitute for lead - in, for example, shot - and its use in pharmaceuticals.With the exception of mercury, bismuth has the lowest thermal conductivityof all metals. Because of this, when mixed with, for example, tellurium (forming, in this instance, bismuth telluride (Bi2Te3)), the resulting compound is a semiconductor. And, as such, bismuth telluride is excellent for making thermoelectric coolers.In addition to having the highest electrical resistance of any metallic element, bismuth also has the highest Hall effect of any metal (i.e.,greatest increase in electrical resistance when placed in a magnetic field). Before cheaper, rare earth, magnets came along, bismuth - together with manganese and iron - was used in a variety of powerful permanent magnets; in particular, "Bismanol" developed by the U.S. Naval Surface Warfare Center.With its low melting point, only some 520.7°F (271.5°C), alloys of bismuth and other metals such ascadmium, iron, tin and lead are used extensively in electrical fuses, fire detection and automatic sprinkler systems. Such an alloy containing bismuth (49.5%), cadmium (11.1%), lead (27.3%) and tin (13.1%) has a melting point of only 70°C. Others have lower melting points, down even to 20°C.Finally, since bismuth, like antimony, expands when it solidifies, alloys of the metal are excellent for makingsharp castings of objects that can be damaged at high temperatures, solders (for use in, for example, plumbing) and holding devices for grinding optical lenses. Whence Bismuth? Source: USGS Little, if any, bismuth is currently derived from bismuth ore. A Bolivian mine that once so produced the metal has been mothballed since the mid-90s. And, in 2008, only some small mines in China produced the metalfrom bismuth ore.For the most part, bismuth is a by-product of processing either lead or tungsten ores. But it can also be extracted from copper-, gold-, silver- and tin-bearing ores.As with so many other metals, China is the world's major source of bismuth, where it is produced, for the most part, as a by-product of processing tungsten ore, but also of tin and fluorspar. Bismuth production in...