Dictionary:

boron

  (bôr'ŏn', bōr'-)

A soft, brown, amorphous or crystalline nonmetallic element, extracted chiefly from kernite and borax and used in flares, propellant mixtures, nuclear reactor control elements, abrasives, and hard metallic alloys. Atomic number 5; atomic weight 10.811; melting point 2,300°C; sublimation point 2,550°C; specific gravity (crystal) 2.34; valence 3.

[BOR(AX)¹ + (CARB)ON.]

A chemical element, B, atomic number 5, atomic weight 10.811, in group III of the periodic table. It has three valence electrons and is nonmetallic in behavior. It is classified as a metalloid and is the only nonmetallic element which has fewer than four electrons in its outer shell. The free element is prepared in crystalline or amorphous form. The crystalline form is an extremely hard, brittle solid. It is of jet-black to silvery-gray color with a metallic luster. One form of crystalline boron is bright red. The amorphous form is less dense than the crystalline and is a dark-brown to black powder. In the naturally occurring compounds, boron exists as a mixture of two stable isotopes with atomic weights of 10 and 11. See also Periodic table.

Many properties of boron have not been sufficiently established experimentally as a result of the questionable purity of some sources of boron, as well as of the variations in the methods and temperatures of preparation. A summary of the physical properties is shown in the table.

Boron and boron compounds have numerous uses in many fields, although elemental boron is employed chiefly in the metal industry. Its extreme reactivity at high temperatures, particularly with oxygen and nitrogen, makes it a suitable metallurgical degasifying agent. It is used to refine the grain of aluminum castings and to facilitate the heat treatment of malleable iron. Boron considerably increases the high-temperature strength characteristics of alloy steels. Elemental boron is used in the atomic reactor and in high-temperature technologies. The physical properties that make boron attractive as a construction material in missile and rocket technology are its low density, extreme hardness, high melting point, and remarkable tensile strength in filament form. When boron fibers are used in an epoxy (or other plastic) carrier material or matrix, the resulting composite is stronger and stiffer than steel and 25% lighter than aluminum. Refined borax, Na₂B₄O₇ · 10H₂O, is an important ingredient of a variety of detergents, soaps, water-softening compounds, laundry starches, adhesives, toilet preparations, cosmetics, talcum powder, and glazed paper. It is also used in fireproofing, disinfecting of fruit and lumber, weed control, and insecticides, as well as in the manufacture of leather, paper, and plastics.

Boron makes up 0.001% of the Earth's crust. It is never found in the uncombined or elementary state in nature. Besides being present to the extent of a few parts per million in sea water, it occurs as a trace element in most soils and is an essential constituent of several rock-forming silicate minerals, such as tourmaline and datolite. The presence of boron in extremely small amounts seems to be necessary in nearly all forms of plant life, but in larger concentrations, it becomes quite toxic to vegetation. Only in a very limited number of localities are high concentrations of boron or large deposits of boron minerals to be found in nature; the more important of these seem to be primarily of volcanic origin.

An element, known to be essential for plant growth, but not known to have any function in human beings or animals. Suggested to modify the actions and metabolism of oestrogens, and sometimes used in preparations to alleviate pre-menstrual syndrome, although there is little evidence of efficacy; toxic in excess. Occurs mainly as salts of boric acid.

An essential mineral for healthy plant growth, boron may also be essential for animals. There is some evidence that, in small amounts, it may reduce calcium loss in post-menopausal women, reducing the risk of osteoporosis, but the evidence is weak and has been challenged.

Description

Boron is a trace mineral that has gained popularity in recent years due to claims that it can strengthen bones, build muscle mass, and boost brain activity. While such macrominerals as calcium, magnesium, and potassium have become household names because they make up over 98% of the body's mineral content, certain trace minerals are also considered essential in very tiny amounts to maintain health and ensure proper functioning of the body. They usually act as coenzymes, working as a team with proteins to facilitate important chemical reactions. While boron is considered essential for plants, it is not known if the mineral is necessary for humans. Evidence has been mounting in the last two decades, however, that suggests boron may be an important micronutrient.

Studies indicate that boron may contribute to the way that calcium, a vital building block of bone, and other minerals are processed by the body. Boron appears to increase the amount of calcium absorbed from food and lower the amount excreted by the body. These effects may help to keep bones strong. Boron may also improve mental functioning, strengthen the immune system, boost energy utilization, and affect cholesterol production. While the effects of a boron-free diet have not been observed in people, animal studies suggest that a lack of boron can be unhealthy. In one investigation, for example, a boron-deficient diet fed to animals seemed to increase the amount of calcium they lost. It also appeared to have a negative effect on bone development and energy utilization. It is not certain, however, that study results such as this confirm the nutritional importance of boron for human beings. As of 2000, research is still necessary to determine if boron can produce significant health benefits safely and effectively. The proper dosage of the mineral has not yet been established.

General Use

While not extensively studied, boron has been touted as having a number of beneficial effects. Some people take it to help treat osteoporosis or arthritis and to alleviate menopausal symptoms. It has been reported to enhance mental activity, memory, and hand-eye coordination. Some body builders and athletes take boron supplements as a muscle-enhancing agent despite the fact that there is no evidence to support this use. Overall, boron appears to have the most potential as a possible bonebuilder and brain booster.

The effects of boron on bone strength were investigated in a small study of 12 postmenopausal women between the ages of 48 and 82, published in the FASEB Journal in 1987. The women had received a low-boron diet (containing about 0.25 mg a day of the mineral) for several months before being given daily boron supplements of 3 mg. Once the women increased their intake of boron, they were able to retain more bone-building minerals such as calcium and magnesium. This effect was greater in women who started out with low levels of magnesium. Boron supplements also significantly increased levels of estrogen and testosterone, especially in the magnesium-deficient group. The results of this study suggest that getting an adequate amount of boron, whether through dietary intake or boron supplements, may help to maintain strong bones by allowing the body to use calcium and other important minerals more efficiently.

Most of the research suggesting that boron may be helpful for arthritis is indirect and circumstantial. Early studies in sheep and chickens indicated that boron may be useful in helping to treat the disease. There is also an interesting relationship between the incidence of arthritis and boron intake in certain geographical locations. In parts of the world where boron intake is high (intake can range anywhere from 3–10 mg), usually as a result of high boron levels in the soil and water, the number of people who develop arthritis tends to be lower than in areas where people consume less of the mineral. Boron levels in the water and soil are usually highest in arid climates, such as the desert regions of the United States and South America, the Red Sea region of the Middle East, and parts of Australia. There are few human studies of boron in relation to arthritis, although one small investigation in people has suggested that boron may help to relieve symptoms of the disease.

While there is some evidence that boron may be helpful in the treatment of postmenopausal osteoporosis, the mineral does not appear to ease the symptoms associated with menopause. In a five-week study involving 46 menopausal women, about 50% of those who received boron supplements experienced more frequent and severe hot flashes (as well as night sweats) and generally had an increase in menopausal symptoms. Over a third of the women who received boron reported that the mineral made no difference at all in their symptoms. Boron had a beneficial effect in only 15% of the women who took it. These findings suggest that boron may actually aggravate menopausal symptoms more often than it alleviates them.

Researchers from the Grand Forks Human Nutrition Research Center, which is affiliated with the United States Department of Agriculture (USDA), investigated the role of boron in brain and psychological function in several studies involving humans and animals. In one study, increasing boron intake in rats receiving a boron-deficient diet seemed to increase mental activity. Studies conducted in people suggested that a lack of boron can decrease mental activity and have a negative effect on hand-eye coordination, the ability to concentrate, and short-term memory. These findings seem to indicate an important role for boron in keeping the brain fit.

The use of boron by body builders stems from its apparent ability to increase testosterone levels. Because testosterone is known to play an important role in the development of muscles, some weight lifters have taken boron supplements because they believe it will increase levels of male hormone and make them stronger. There is no evidence, however, that boron can increase muscle mass or athletic performance. Boron supplements are generally not considered effective as a muscle-enhancing agent.

Preparations

A recommended daily allowance (RDA) for boron has not been established. The estimated dosage of boron, which is available as an over-the-counter dietary supplement, is generally 3 mg a day. Even without taking supplements, most people get anywhere from 1–3 mg of boron through their diets. For this reason, some authorities suggest avoiding boron supplements altogether and eating foods known to contain the mineral. Good sources of boron include fruits, especially pears, apples, peaches, grapes, and raisins; leafy vegetables; peanuts and other nuts; and beans. Beer and wine also contain boron. Drinking water can be a good source of the mineral depending on geographical location. Getting too much of the mineral through food and drink is not considered a significant risk because boron is present only in very small amounts in plants and animals.

Precautions

Boron is not known to be harmful when taken in recommended dosages, though there are some precautions to consider. Boron appears to increase estrogen levels, especially in women receiving estrogen therapy. For this reason, women receiving hormone therapy should talk to their doctors before taking boron supplements. Combining the mineral with estrogen drugs may result in elevated and potentially unhealthy levels of female hormone. However, it is considered safe for women on estrogen therapy to eat boron-containing foods. In fact, many of the fruits and vegetables containing the mineral are believed to contribute to good health.

The long-term health risks associated with taking boron supplements are unknown.

Side Effects

When taken in recommended dosages, boron has not been associated with any significant or bothersome side effects. At very high dosages, boron may cause nausea and vomiting, diarrhea, and headaches.

Interactions

Combining boron and estrogen-containing drugs may cause an undesirable increase in estrogen levels.

Resources

Books

Sifton, David W. PDR Family Guide to Natural Medicines and Healing Therapies. New York: Three Rivers Press, 1999.

Periodicals

Nielsen F.H., C.D. Hunt, and L.M. Mullen, et al. "Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women." FASEB Journal (1987): 394-7.

Organizations

Grand Forks Human Nutrition Research Center. 2420 2nd Ave North. Grand Forks, ND 58202.

Other

Discovery Health. .

[Article by: Greg Annussek]

For more information on boron, visit Britannica.com.

A non-metallic element essential for the proper health of plants, but it is not known what nutritional value, if any, it has for humans. Nevertheless, boron is included in some sport nutritional supplements as a means of increasing serum testosterone levels, thereby promoting anabolism. Current research indicates boron supplements have no effect on serum testosterone levels, lean body mass, or strength in strength-trained individuals.

A chemical element, atomic number 5, atomic weight 10.811, symbol B.

5 beryllium ← boron → carbon - ↑ B ↓ Al Periodic table - Extended periodic table
General
Name, symbol, number	boron, B, 5
Chemical series	metalloids
Group, period, block	13, 2, p
Appearance	black/brown
Standard atomic weight	10.811(7) g·mol−1
Electron configuration	1s2 2s2 2p1
Electrons per shell	2, 3
Physical properties
Phase	solid
Density (near r.t.)	2.34 g·cm−3
Liquid density at m.p.	2.08 g·cm−3
Melting point	2349 K (2076 °C, 3769 °F)
Boiling point	4200 K (3927 °C, 7101 °F)
Heat of fusion	50.2 kJ·mol−1
Heat of vaporization	480 kJ·mol−1
Heat capacity	(25 °C) 11.087 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 2348 2562 2822 3141 3545 4072
Atomic properties
Crystal structure	rhombohedral
Oxidation states	3 (mildly acidic oxide)
Electronegativity	2.04 (Pauling scale)
Ionization energies (more)	1st: 800.6 kJ·mol−1
	2nd: 2427.1 kJ·mol−1
	3rd: 3659.7 kJ·mol−1
Atomic radius	85 pm
Atomic radius (calc.)	87 pm
Covalent radius	82 pm
Miscellaneous
Magnetic ordering	nonmagnetic
Electrical resistivity	(20 °C) 1.5×104Ω·m
Thermal conductivity	(300 K) 27.4 W·m−1·K−1
Thermal expansion	(25 °C) 5–7 µm·m−1·K−1
Speed of sound (thin rod)	(20 °C) 16200 m/s
Bulk modulus	(β form) 185 GPa
Mohs hardness	9.3
Vickers hardness	49000 MPa
CAS registry number	7440-42-8
Selected isotopes
Main article: Isotopes of boron iso NA half-life DM DE (MeV) DP 10B 18.8%* B is stable with 5 neutrons 11B 81.2%* B is stable with 6 neutrons *Boron-10 content may be as low as 19.1% and as high as 20.3% in natural samples. Boron-11 is the remainder in such cases.
References

Boron (IPA: /ˈbɔːrɒn/) is a chemical element with atomic number 5 and the chemical symbol B. A trivalent compound containing boron occurs abundantly in the ore borax. Boron is never found free in nature, and is a metalloid.

Several allotropes of boron exist; amorphous boron is a brown powder, though crystalline boron is black, hard (9.3 on Mohs' scale), and a weak conductor at room temperature.

Elemental boron is used as a dopant in the semiconductor industry, while boron compounds play important roles as light structural materials, nontoxic insecticides and preservatives, and reagents for chemical synthesis.

Boron is an essential plant nutrient, although soil concentrations of > 1.0 ppm can cause marginal and tip necrosis in leaves as well as poor overall growth performance. Levels as low as 0.8 ppm can cause these same symptoms to appear in plants particularly sensitive to boron in the soil. Nearly all plants, even those somewhat tolerant of boron in the soil, will show at least some symptoms of boron toxicity when boron in the soil is greater than 1.8 ppm. When boron in the soil exceeds 2.0 ppm, few plants will perform well. Plants sensitive to boron in the soil may not survive. When boron levels in plant tissue exceed 200 ppm symptoms of boron toxicity are likely to appear. As an ultratrace element, boron is necessary for the optimal health of animals, though its physiological role in animals is poorly understood.

Characteristics

Brown amorphous boron is a product of certain chemical reactions. It contains boron atoms randomly bonded to each other without long range order.

Crystalline boron, a very hard black material with a high melting point, exists in many polymorphs. Two rhombohedral forms, α-boron and β-boron containing 12 and 106.7 atoms in the rhombohedral unit cell respectively, and 50-atom tetragonal boron are the three most characterised crystalline forms.

Optical characteristics of crystalline/elemental boron include the transmittance of infrared light. At standard temperatures, elemental boron is a poor electrical conductor, but is a good electrical conductor at high temperatures.

Chemically boron is electron-deficient, possessing a vacant p-orbital. It is an electrophile. Compounds of boron often behave as Lewis acids, readily bonding with electron-rich substances to compensate for boron's electron deficiency. The reactions of boron are dominated by such requirement for electrons. Also, boron is the least electronegative non-metal, meaning that it is usually oxidized (loses electrons) in reactions.

Boron is also similar to carbon with its capability to form stable covalently bonded molecular networks. Boron is also used for heat resistant alloys.

Applications

• In automobiles: it is proposed that by reacting water with the element, hydrogen could be produced to be burnt in an internal combustion engine or fed to a fuel cell to generate electricity.^[1]

¹⁰B and ¹¹B NMR spectroscopy

Both ¹⁰B (18.8 percent) and ¹¹B (81.2 percent) possess nuclear spin; that of boron-10 has a value of 3 and that of boron-11, 3/2. These isotopes are, therefore, of use in nuclear magnetic resonance spectroscopy; and spectrometers specially adapted to detecting the boron-11 nucleus are available commercially. The boron-10 and boron-11 nuclei also cause splitting in the resonances of attached nuclei.

B-10 depleted boron

The ¹⁰B isotope is good at capturing thermal neutrons from cosmic radiation. It then undergoes fission - producing a gamma ray, an alpha particle, and a lithium ion. When this happens inside of an integrated circuit, the fission products may then dump charge into nearby chip structures, causing data loss (bit flipping, or single event upset). In critical semiconductor designs, depleted boron—consisting almost entirely of ¹¹B—is used to avoid this effect, as one of radiation hardening measures. ¹¹B is a by-product of the nuclear industry. ¹¹boron is also a candidate as a fuel for aneutronic fusion.

B-10 enriched boron

The ¹⁰B isotope is good at capturing thermal neutrons, and this quality has been used in both radiation shielding and in boron neutron capture therapy where a tumor is treated with a compound containing ¹⁰B is attached to a muscle, and the patient treated with a relatively low dose of thermal neutrons which go on to cause energetic and short range alpha radiation in the tissue treated with the boron isotope.

Neutron cross section of boron (Black is ¹⁰B and blue is ¹¹B)

In nuclear reactors, ¹⁰B is used for reactivity control and in emergency shutdown systems. It can serve either function in the form of borosilicate rods or as boric acid. In pressurized water reactors, boric acid is added to the reactor coolant when the plant is shut down for refueling. It is then slowly filtered out over many months as fissile material is used up and the fuel becomes less reactive.

In future manned interplanetary spacecraft, ¹⁰B has a theoretical role as structural material (as boron fibers or BN nanotube material) which also would serve a special role in the radiation shield. One of the difficulties in dealing with cosmic rays which are mostly high energy protons, is that some secondary radiation from interaction of cosmic rays and spacecraft structural materials, is high energy spallation neutrons. Such neutrons can be moderated by materials high in light elements such as structural polyethylene, but the moderated neutrons continue to be a radiation hazard unless actively absorbed in a way which dumps the absorption energy in the shielding, far away from biological systems. Among light elements that absorb thermal neutrons, ⁶Li and ¹⁰B appear as potential spacecraft structural materials able to do double duty in this regard.

Market trend

Estimated global consumption of boron rose to a record 1.8 million tonnes of B₂O₃ in 2005 following a period of strong growth in demand from Asia, Europe and North America. Boron mining and refining capacities are considered to be adequate to meet expected levels of growth through the next decade. The form in which boron is consumed has changed in recent years. The use of beneficiated ores like colemanite has declined following concerns over arsenic content. Consumers have moved towards the use of refined borates or boric acid that have a lower pollutant content.

Increasing demand for boric acid has led a number of producers to invest in additional capacity. Eti Mine opened a new 100,000 tonnes per year capacity boric acid plant at Emet in 2003. Rio Tinto increased the capacity of its Boron plant from 260,000 tonnes per year in 2003 to 310,000 tonnes per year by May 2005, with plans to grow this to 366,000 tonnes per year in 2006.

Chinese boron producers have been unable to meet rapidly growing demand for high quality borates. This has led to imports of disodium tetraborate growing by a hundredfold between 2000 and 2005 and boric acid imports increasing by 28% per year over the same period.

The rise in global demand has been driven by high rates of growth in fiberglass and borosilicate production. A rapid increase in the manufacture of reinforcement-grade fiberglass in Asia with a consequent increase in demand for borates has offset the development of boron-free reinforcement-grade fiberglass in Europe and the USA. The recent rises in energy prices can be expected to lead to greater use of insulation-grade fiberglass, with consequent growth in the use of boron.

Roskill Consulting Group forecasts that world demand for boron will grow by 3.4% per year to reach 21 million tonnes by 2010. The highest growth in demand is expected to be in Asia where demand could rise by an average 5.7% per year.^[2]

Boron compounds

The most economically important compounds of boron are:

• Sodium tetraborate pentahydrate (Na₂B₄O₇ · 5H₂O), which is used in large amounts in making insulating fiberglass and sodium perborate bleach,
• Orthoboric acid (H₃BO₃) or boric acid, used in the production of textile fiberglass and flat panel displays or eye drops, among many uses, and
• Sodium tetraborate decahydrate (Na₂B₄O₇ · 10H₂O) or borax, used in the production of adhesives, in anti-corrosion systems and many other uses.
• Boron nitride is a material in which the extra electron of nitrogen (with respect to carbon) in some ways compensates for boron's deficiency of an electron.
• Boron reacts with ammonia at high temperatures to give a compound called borazole (B₃N₃H₆), also known as inorganic benzene.

Of the several hundred uses of boron compounds, especially notable uses include:

• Boron is an essential plant micronutrient.
• Because of its distinctive green flame, amorphous boron is used in pyrotechnic flares.
• Boric acid is an important compound used in textile products.
• Boric acid is also traditionally used as an insecticide, notably against ants, fleas, and cockroaches.
• Borax is sometimes found in laundry detergent.
• Boron filaments are high-strength, lightweight materials that are chiefly used for advanced aerospace structures as a component of composite materials, as well as limited production consumer and sporting goods such as golf clubs and fishing rods.
• Boron is used as a melting point depressant in nickel-chromium braze alloys.
• Boron slurry is used as an energetic material with very high energy density like rocket fuels and jet engines.
• Boron compounds show promise in treating arthritis.

History

Compounds of boron (Arabic Buraq from Persian Burah from Turkish Bor) have been known of for thousands of years. In early Egypt, mummification depended upon an ore known as natron, which contained borates as well as some other common salts. Borax glazes were used in China from 300 AD, and boron compounds were used in glassmaking in ancient Rome.

The element was not isolated until 1808 by Sir Humphry Davy, Joseph Louis Gay-Lussac, and Louis Jacques Thénard, to about 50 percent purity, by the reduction of boric acid with sodium or magnesium. These men did not recognize the substance as an element. It was Jöns Jakob Berzelius in 1824 who identified boron as an element. The first pure boron was produced by the American chemist W. Weintraub in 1909, although this is disputed by some researchers.^[3]

It is thought that boron plays several biochemical roles in animals, including humans.^[4]

Occurrence

Turkey and the United States are the world's largest producers of boron. Turkey has almost 63% of the world’s boron potential and boron reserves.^[5] Boron does not appear in nature in elemental form but is found combined in borax, boric acid, colemanite, kernite, ulexite and borates. Boric acid is sometimes found in volcanic spring waters. Ulexite is a borate mineral that naturally has properties of fiber optics.

Borax crystals

Economically important sources are from the ore rasorite (kernite) and tincal (borax ore) which are both found in the Mojave Desert of California, with borax being the most important source there. The largest borax deposits are found in Central and Western Turkey including the provinces of Eskişehir, Kütahya and Balıkesir.

Even a boron-containing natural antibiotic, boromycin, isolated from streptomyces, is known.^[6][7]

Pure elemental boron is not easy to prepare. The earliest methods used involve reduction of boric oxide with metals such as magnesium or aluminium. However the product is almost always contaminated with metal borides. (The reaction is quite spectacular though.) Pure boron can be prepared by reducing volatile boron halogenides with hydrogen at high temperatures. The highly pure boron, for the use in semiconductor industry, is produced by the decomposition of diborane at high temperatures and then further purified with the Czochralski process.

Food

Boron occurs in all foods produced by plants. Since 1989 its nutritional value has been argued. The U.S. Department of agriculture conducted an experiment in which postmenopausal women took 3 mg of boron a day. The results showed that boron can drop excretion of calcium by 44%, and activate estrogen and vitamin D.

The US National Institute of Health quotes this source:

Total daily boron intake in normal human diets ranges from 2.1–4.3 mg boron/kg body weight (bw)/day. "Total boron". Zook EG and Lehman J. J. Assoc. Off Agric. Chem. 48: 850-5 (1965).

See also: Borate minerals.

Analytical quantification

For determination of boron content in food or materials the colorimetric curcumin method is used. Boron has to be transferred to boric acid or borates and on reaction with curcumin in acidic solution a red colored boron-chelate complex, rosocyanine, is formed.

Isotopes

Boron has two naturally-occurring and stable isotopes, ¹¹B (80.1%) and ¹⁰B (19.9%). The mass difference results in a wide range of δ¹¹B values in natural waters, ranging from -16 to +59. There are 13 known isotopes of boron, the shortest-lived isotope is ⁷B which decays through proton emission and alpha decay. It has a half-life of 3.26500x10^-22 s. Isotopic fractionation of boron is controlled by the exchange reactions of the boron species B(OH)₃ and B(OH)₄. Boron isotopes are also fractionated during mineral crystallization, during H₂O phase changes in hydrothermal systems, and during hydrothermal alteration of rock. The latter effect species preferential removal of the ¹⁰B(OH)₄ ion onto clays results in solutions enriched in ¹¹B(OH)₃ may be responsible for the large ¹¹B enrichment in seawater relative to both oceanic crust and continental crust; this difference may act as an isotopic signature.

The exotic ¹⁷B exhibits a Nuclear halo.

Precautions

Elemental boron is nontoxic and common boron compounds such as borates and boric acid have low toxicity (approximately similar to table salt with the lethal dose being 2 to 3 grams per kg) and therefore do not require special precautions while handling. Some of the more exotic boron hydrogen compounds, however, are toxic as well as highly flammable and do require special handling care.

See also

• Boron deficiency
• Boronic acid
• Suzuki coupling
• Hydroboration-oxidation reaction
• Boron compounds

References

1. ^ http://www.newscientisttech.com/channel/tech/mg19125621.200
2. ^ http://www.roskill.com/reports/prePublication/prepubboron
3. ^ (1970) "". Z. Angew. Phys. 29: 277. 
4. ^ http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/bor_0040.shtml
5. ^ http://www.byegm.gov.tr/YAYINLARIMIZ/kitaplar/turkiye2006/english/302-303.htm
6. ^ Hütter (1967). "". Helv. Chim. Acta. 50: 1533–1539. 
7. ^ Dunitz (1971). "". Helv. Chim. Acta. 54: 1709–1713. 

• Los Alamos National Laboratory – Boron

External links

Wikimedia Commons has media related to:

Boron

• Boron
• Computational Chemistry Wiki
• Environmental Health Criteria 204: Boron (1998) by the IPCS.
• It's Elemental – Boron
• National Pollutant Inventory - Boron and compounds
• WebElements.com – Boronnov:Borezh-yue:硼

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