Boron is a nonmetallic element with the atomic number 5, identified by the symbol B on the periodic table. There are a number of uses for boron, and like many elements, it appears in various forms which have different potential applications. Pure elemental boron, however, is not found in nature, and it must be chemically extracted. One of the more well known uses for a form of boron is borax, a chemical compound which contains boron.
The pure form of boron is black and crystalline in form, and extremely brittle. A more common variant of the element is an amorphous form, which is soft, brown, and crumbly. Boron is often used in metal refining, because it is reactive at high temperatures. Although boron is nonmetallic, it is classified as a metalloid. Metalloids are elements which share certain properties with metals, making them useful in alloys and compounds used to chemically manipulate metals.
As is the case with many elements which do not occur naturally in elemental form, it took some time for scientists to isolate it. In 1808, several scientists succeeded in isolating a form of boron, although they did not recognize it as an element. In the early 1900s, chemists succeeded in creating pure boron, realizing more potential applications for the element. Methods for isolation are not widely standardized, leading to varying quality when it comes to pure boron.
Plants require boron in trace amounts to be healthy, although the threshold between enough boron and too much is rather small. Humans and animals also ingest small amounts of boron through the plants that they eat, but it is not believed to be a necessary trace element in human nutrition. Boron is also used in a range of industries, as a dopant, abrasive, and ingredient in propellant mixtures, among other things.
Pure boron is not itself harmful, although many of the forms in which it appears are toxic or somewhat toxic. It may naturally appear in blends of toxic material, which can make handling some forms of boron rather harmful. In addition, boron extraction generates harmful waste, since it must be heavily treated to extract a usable pure form. Even when this material is handled responsibly, it represents a potential environmental problem, as toxins are difficult to break down into a safe and stable form. Mining companies may try to cut corners with their toxic waste, generating a major pollution problem.
Boron, although not one of the commoner elements on the Earth as a whole, exists in the form of large, easily accessible deposits of boron minerals in a number of areas, rendering it readily available. Usually, these deposits occur in dry areas and contain the element in the form of water-soluble borates. Elemental boron has few commercial applications, but the uses of boron compounds, such as borates, are many and varied. They are found in industrial processes, manufactured products and in medicine.
One of the earliest uses of boron, in the form of borates, was in pottery, where it combined with silicates to form a hard, transparent glaze. Today, one of the most important uses of boron is in the production of borosilicate glass. This type of glass is notable for undergoing very little expansion when heated. It is therefore unlikely to crack when subjected to rapid heating or cooling, and ideally suited to use in laboratory glassware and in cookware. One well-known brand of glassware is particularly associated with these applications.
Boron is an essential element for plants, and may be added in small amounts to fertilizers for use in boron-deficient areas; too much boron, however, is toxic. Its role, if any, in animals has not been clearly identified. The element enters the metabolism through ingested food, usually in the form of borates, and although there are no known cases of boron deficiency in humans, it may be required in trace amounts. A number of benefits have been claimed for boron supplements in the diet, but evidence in support of these is inconclusive.
Boron compounds have low toxicity to humans and other mammals, but are very toxic to many insects, especially ants and cockroaches. A number of commercial insecticides contain boric acid or other boron compounds. Boric acid is also widely used as an antiseptic, an eyewash and as a treatment for some yeast infections. It is a very weak acid and does not cause irritation of the skin or eyes.
Another of the uses of boron in medicine is in a cancer treatment known as Boron Neutron Capture Therapy (BNCT). The treatment involves introducing the stable isotope boron-10 into cancer cells. This boron isotope can absorb neutrons that cause it to produce an alpha particle and a lithium ion. These particles carry a lot of energy, but do not travel far; all their energy is released within the target cell, damaging it, but leaving adjacent cells unharmed. It is thus possible to destroy tumors by adding boron-10 to a compound that is absorbed more readily by cancerous cells, then bombarding the tumor with neutrons.
In industry, one of the major of the uses of boron is in abrasives and cutting tools. Two compounds of boron, boron carbide (B4C) and boron nitride (BN) are notable for their extreme hardness. Boron nitride resembles carbon in that it can have a graphite-like hexagonal form and also a diamond like structure. The hexagonal form is used in lubricants. Like carbon, it can also be made into nanotubes and nanoribbons, whose electrical, magnetic and optical properties show a lot of promise for various electronic applications.
Boron-10, because of its ability to absorb neutrons without forming radioactive isotopes, is used for shielding purposes in nuclear reactors. Neodymium magnets also contain boron. Borates are used in a number of household cleaning and laundry products to soften hard water, in fire retardants and as a green flame colorant in pyrotechnics and emergency flares.