Bismuth, chemical symbol Bi, is a chemical element whose atomic number is 83. This chemical element is actually a pentavalent post-transition metal and is among the pnictogens (belonging to the elements in the nitrogen group). The chemical properties of bismuth are similar to its lighter homologs such as antimony and arsenic. While rudimentary bismuth occurs naturally in the Earth’s crust, commercial extraction of this metal is done from its oxide and sulfide ores.
In its pure form, bismuth is very dense, about 86 percent – similar to lead. When produced, this metal has a silvery white color and is brittle. However, oxidation of the metal’s surface can turn its color to somewhat pink. Bismuth is slightly radioactive and is the most diamagnetic naturally occurring element. Among all metals, it is said to have the lowest thermal conductivity.
For long, it was believed that bismuth had the maximum atomic mass making it a stable element. However, it was discovered in 2003 that bismuth has very weak radioactivity and its sole primal isotope – bismuth-209, decompose by means of alpha decay having a half-life of over a billion times that of the projected age of the universe. As a result of the element’s immensely long half-life, still bismuth may be regarded as stable for just about all functions.
As a metal, bismuth has been known to people since primeval times. However, people often confused bismuth with tin or lead, whose properties are similar to that of this metallic element. While the etymology is in doubt, bismuth possibly derived its name from the Arabic term bi ismid, which denotes possessing the attributes of antimony. Another view is that bismuth may have got its name from the German words wismuth (meaning “white mass”) or weiße masse, which was translated to new Latin bisemutum in the mid-sixteenth century.
Almost 50 percent bismuth is produced from the various compounds of bismuth. They have a wide variety of uses – for instance in pigments, cosmetics and even some pharmaceuticals. It is worth mentioning here that bismuth subsalicylate is a constituent of medications prescribed for treating diarrhea. When frozen, bismuth has an unusual tendency to expand. This property of the metal makes it useful in some applications, such as in printing type casting. Despite being a heavy metal, bismuth has a strangely low level of toxicity. With the high toxicity of lead becoming more and more apparent these days, use of bismuth alloys has seen a remarkable rise in a number of applications. Currently, about a third of the total production of bismuth is used in the form of a substitute for lead.
An unidentified alchemist discovered bismuth sometime around 1400 AD. For almost a century after its discovery, bismuth has been mostly used in the form of an alloying agent for caskets and cast types of printers. A German mineralogist named Georgius Agricola was the first to recognize the discrete properties of bismuth in the early 1500s. Incidentally, a German professor named Caspar Neuman analyzed bismuth and found the same distinct properties of this metallic element almost two centuries later – in the early 1700s. Eventually in 1753, a French chemist named Claude-Francois Geoffroy provided more evidences asserting the presence of a new metallic element – bismuth.
There are a number of chemical applications of bismuth. In nearly all these chemical applications bismuth is used in very small quantities compared to the other raw materials.
In the U.S., a number of potable water system manufacturers have been replacing lead with bismuth to make valves etc. with a view to fulfil the “lead-free” regulations that came into effect in 2014. This is a major use of bismuth considering the fact that it covers the entire residential as well as commercial building complexes.
It was as late as the early 1990s that some scientists started evaluating this metallic element as non-toxic substitute of lead in different applications.
Shells of shotguns made of bismuth are used to reload hunting rifles and revolvers. This is because bismuth is less expensive compared to ammunitions made of tungsten and lead, but have the same attributes. Another application of bismuth is in the manufacture of magnetic levitation devices. Bismuth also has medical use. Tablets made of an insoluble trivalent bismuth salt together with bismuth subsalicylate and salicylic acid is given to people suffering from nausea, heartburn and stomach disorders. Chewing these tablets helps to treat the disorders.
Combining metals like zinc, copper, lead with bismuth produces an alloy known as bismuth bronze. Bismuth (Bi) and this alloy used for casting of lamps, mirrors and reflectors. Since the electrical resistance of bismuth is very high, the oxides of this element’s nano-particles are used in cancer imaging and in the form of cathodes in the solid fuel cells. Moreover, these nano-particles are an excellent replacement of lead, especially for manufacturing sinkers, water pipes, fishing weights and solders paste. These days, in many places glasses containing lead are being replaced with Bi-based glasses as their toxicity is much less.
This metal is used to electroplate baths that have a vital role in the manufacture of bearing for diesel and gasoline engines. Bi crystals have applications in the jewellery industry and they are also used in jewellery such as necklaces and rings. Although its use in pharmacy is gradually on the decline, some manufacturers still use bismuth in specific medications.
A compound of this metal – bismuth subsalicylate possesses anti-diarrheal properties and is often blended with other substances to make tablets for treating nausea and upset stomach. However, the anti-bacterial attribute of bismuth subsalicylate is yet to be properly understood and documented by scientists. It is believed that in some instances there may be an oligodynamic effect (in other words, the effects of toxic substances present in heavy metal ions on microorganism when they are taken in small doses) when bismuth subsalicylate is used for treating diarrhea or nausea. Salicylic acid prepared from this compound by means of hydrolysis has been found to have anti-microbial effect on the toxic consequences of E. coli – a common pathogen found in diarrhea suffered by travelers.
A mixture of two bismuth compounds – bismuth subcitrate and bismuth subsalicylate, is used for eliminating the bacteria responsible for peptic ulcers. A compound called bibrocathol contains organic bismuth and it is used for treating infections of the eyes. Another bismuth compound – bismuth subgallate forms an active ingredient of a medication, Devrom, which is used in the form of an internal deodorant for treating malodor emitted by feces and flatulence.
Earlier, a number of compounds of bismuth, such as sodium bismuth tartrate, were used for curing syphilis. In fact, in the early part of the 20th century a substance called “milk of bismuth” (a watered suspension containing bismuth subcarbonate and bismuth hydroxide) was sold as a nourishing panacea. Even today bismuth compounds such as bismuth subcarbonate and bismuth subnitrate are still used in various medications.
Occasionally, manufacturers use bismuth oxychloride in cosmetics, especially in the form of a pigment in nail polishes, hair sprays and eye shadows. This bismuth compound occurs in the form of a mineral known as bismoclite and when present in crystal form it comprises layers of atoms, which chromatically refract light thereby producing manifesting an iridescent that resembles a pearl’s nacre (organic-inorganic compound material turned out by various molluscs forming an internal shell layer, which is often called the mother of pearl). In ancient Egypt and later in many other places, it was used in the form of a cosmetic. When we talk about “bismuth white” (also known as “Spanish white”) it means either bismuth oxynitrate or bismuth oxychloride, especially when it is used in the form of a white pigment.
Another compound of this metal, bismuth vanadate, is used in the form of a non-reactive, light-stable paint coloring, especially in paints used by artists. It is often used as a substitute for the yellow and yellowish-orange hued cadmium sulfide, which is comparatively more toxic. The commonest type of paints used by artists is lemon yellow, which cannot be differentiated visually from its substitute containing cadmium, which is also relatively more toxic.
In addition to the above mentioned applications of bismuth, compounds of this metal are often used in the form of catalysts in the process involved in manufacturing rubber and synthetic fiber. Combining bismuth with other metals like iron, lead, tin and cadmium produces alloys that melt in low temperatures. Owing to the low melting points of these alloys they are ideal for use in fire extinguishers and fire detectors. Bismuth alloys are also employed to make objects having sharp castings, which are vulnerable to damage when exposed to high temperatures. This is primarily owing to the fact that bismuth, which is a liquid metal, increases 3.32 percent when it is solidified. This metal can be used to produce transuranium elements by means of a process known as cold fusion. In addition, bismuth also has a role in nuclear reactors.