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In 1808, Sir Humphry Davy and J. L. Gay-Lussac discovered boron. It is a trivalent, nonmetallic element that occurs abundantly in the evaporite ores, borax and ulexite. Boron is never found as a free element on Earth. Boron as a crystalline is a very hard, black material with a high melting point, and exists in many polymorphs. Boron has several forms, the most common form being amorphous boron, a dark powder, non-reactive to oxygen, water, acids, and alkalis. It reacts with metals to form borides. Boron is an essential plant micronutrient. Sodium borate is used in biochemical and chemical laboratories to make buffers. Boric acid is produced mainly from borate minerals by the reaction with sulfuric acid. Boric acid is an important compound used in textile products. Compounds of boron are used in organic synthesis, in the manufacture of special types of glasses, and as wood preservatives. Boron fi laments are used for advanced aerospace structures owing to their high strength and light weight. It is used as an antiseptic for minor burns or cuts and is sometimes used in dressings. Boric acid was fi rst registered in the United States in 1948 as an insecticide for control of cockroaches, termites, fi re ants, fl eas, silverfi sh, and many other insects. It acts as a stomach poison affecting the insects’ metabolism, and the dry powder is abrasive to the insects’ exoskeleton. Boric acid is generally considered to be safe for use in household kitchens to control cockroaches and ants. The important use of metallic boron is as boron fi ber. Borate-containing minerals are mined and processed to produce borates for several industrial uses, i.e., glass and ceramics, soaps and detergents, fi re retardants and pesticides. The fi bers are used to reinforce the fuselage of fi ghter aircraft, e.g., the B-1 bomber. The fi bers are produced by vapor deposition of boron on a tungsten fi lament. Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915. Originally, Pyrex was made from thermal shock-resistant borosilicate glass. The common borate compounds include boric acid, sodium tetraborates (Borax), and boron oxide

In nuclear chemistry as neutron absorber, in Ignitron rectifiers, in alloys, usually to harden other metals.

Very toxic; industrial poison; causes depression of the circulation; persistent vomiting; diarrhea; shock and coma.

Boron has been studied extensively for its nutritional importance in animals and humans. There is a growing body of evidence that boron may be an essential element in animals and humans. Many nutritionists believe that people would benefi t from more boron and many popular multivitamins, such as centrum, in the diet. The adverse health effects of boron on humans is limited. However, ingestion/inhalation causes irritation to the mucous membrane and boron poisoning. Short-term exposures to boron in work areas are known to cause irritation of the eye, the upper respiratory tract, and the naso-pharynx, but the irritation disappears with the stoppage of further exposure. Ingestion of large amounts of boron (about 30 g of boric acid)over short periods of time is known to affect the stomach, intestines, liver, kidney, and brain and can eventually lead to death in exposed people.

Boron is used in metallurgy as a degasifying agent and is alloyed with aluminum, iron, and steel to increase hardness. It is also a neutron absorber in nuclear reactors. Boron is frequently encountered in a variety of chemical formulations including boric acid, various borate salts, borax, and boron soil supplements.

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Boron powder or dust: UN3178 Flammable solid, inorganic, Hazard Class: 4.1; Labels: 4.1—Flammable solid.

Boron dust may form explosive mixture in air. Contact with strong oxidizers may cause explosions. Violent reaction (possible explosion) with concentrated nitric acid, hydrogen iodide; silver fluoride. Boron is incompatible with ammonia, bromine tetrafluoride, cesium carbide, chlorine, fluorine, interhalogens, iodic acid, lead dioxide, nitric acid, nitrosyl fluoride, nitrous oxide, potassium nitrite, rubidium carbide. Reacts exothermically with metals at high temperature above 900° C.

Dispose of contents and container to an approved waste disposal plant. All federal, state, and local environmental regulations must be observed.

Boron has only three electrons in its outer shell, which makes it more metal than nonmetal.Nonmetals have four or more electrons in their valence shell. Even so, boron is somewhatrelated to metalloids and also to nonmetals in period 2.
It is never found in its free, pure form in nature. Although less reactive than the metalswith fewer electrons in their outer orbits, boron is usually compounded with oxygen andsodium, along with water, and in this compound, it is referred to as borax. It is also found asa hard, brittle, dark-brown substance with a metallic luster, as an amorphous powder, or asshiny-black crystals.
Its melting point is 2,079°C, its boiling point is 2,550°C, and its density is 2.37 g/cm³.

There are a total of 13 isotopes of boron, two of which are stable. The stableisotope B-10 provides 19.85% of the element’s abundance as found in the Earth’s crust,and the isotope B-11 provides 80.2% of boron’s abundance on Earth.

It is named after the Arabic word bawraq, which means “white borax.”

Boron is the 38th most abundant element on Earth. It makes up about 0.001% of theEarth’s crust, or 10 parts per million, which is about the same abundance as lead. It is notfound as a free element in nature but rather in the mineral borax, which is a compound ofhydrated sodium, hydrogen, and water. Borax is found in salty lakes, dry lake-beds, or alkalisoils. Other naturally occurring compounds are either red crystalline or less dense, dark-brownor black powder.
Boron is also found in kernite, colemanite, and ulexite ores, and is mined in many countries,including the western United States.

Boron is a semimetal, sometimes classed as a metallic or metalloid or even as a nonmetal.It resembles carbon more closely than aluminum. Although it is extremely hard in its purified form—almost as hard asdiamonds—it is more brittle than diamonds, thus limiting its usefulness. It is an excellentconductor of electricity at high temperatures, but acts as an insulator at lower temperatures.

Boron may be prepared by several methods, such as chemical reduction of boron compounds, electrolytic reduction in nonaqueous phase, or by thermal decomposition. Many boron compounds including boron oxides, borates, boron halides, borohydrides, and fluoroborates can be reduced to boron by a reactive metal or hydrogen at high temperatures:
B2O₃ + 3Ca → 2B + 3CaO
The metal is obtained as a black amorphous product.
2BCl₃ + 3H₂ → 2B + 6HCl
High purity grade boron may be prepared by such hydrogen reduction at high temperatures using a hot filament.
Electrolytic reduction and thermal decomposition have not yet been applied in large scale commercial methods. Electrolysis of alkali or alkaline earth borates produces boron in low purity. Electrolytic reduction of fused melts of boron trioxide or potassium tetrafluroborate in potassium chloride yield boron in high purity. Also, boron tribromide or boron hydrides may be thermally dissociated by heating at elevated temperatures.
Impurities from boron may be removed by successive recrystallization or volatilization at high temperatures. Removal of certain impurities such as oxygen, nitrogen, hydrogen or carbon from boron are more difficult and involve more complex steps.

Commercial boron is produced in several ways. (1) Reduction with metals from the abundant B2O3, using lithium, sodium, potassium, magnesium, beryllium, calcium, or aluminum. The reaction is exothermic. Magnesium is the most effective reductant. With magnesium, a brown powder of approximately 90–95% purity is produced. (2) By reduction with compounds, such as calcium carbide or tungsten carbide, or with hydrogen in an electric arc furnace. The starting boron source may be B2O3 or BCl3. (3) Reduction of gaseous compounds with hydrogen. In an atmosphere of a boron halide, metallic filaments or bars at a surface temperature of about 1200 °C will receive depositions of boron upon admission of hydrogen to the process atmosphere. Although the deposition rate is low, boron of high purity can be obtained because careful control over the purity of the starting ingredients is possible. (4) Thermal decomposition of boron compounds, such as the boranes (very poisonous). Boranes in combination with oxygen or H2O are very reactive. In this process, boron halides, boron sulfide, some borides, boron phosphide, sodium borate and potassium borate also can be decomposed thermally. (5) Electrochemical reduction of boron compounds where the smeltings of metallic fluoroborates or metallic borates are electrolytically decomposed. Boron oxide alkali metal oxide–alkali chloride compounds also can be decomposed in this manner.
Elemental boron has found limited use to date in semiconductor applications, although it does possess current-voltage characteristics that make it suitable for use as an electrical switching device. In a limited way, boron also is used as a dopant (p-type) for p?n junctions in silicon. The principal problem deterring the larger use of boron as a semiconductor is the high-lattice defect concentration in the crystals currently available.

Until the late 1990s elemental boron had not found widespread use in industry, where cost of production was a major obstacle. Now, there is increasing use as new applications for the element are developed in material composites and use in nanotechnology.

Nonflammable

Boron (B) is a non-metal occupying the first period and Group 13 (formerly, Ⅲ B) of the Periodic Table. Boron is essential for the growth of new cells. Its concentration in monocots and dicots varies between 6 to 18 ppm and 20 to 60 ppm, respectively. In most crops, the concentration of boron in mature leaf tissue is over 20 ppm.
Boron is one of the seven micronutrients needed by plants. It exists in soils as a (a) primary rock and mineral, (b) mass combined in soil organic matter or adsorbed on colloidal clay and hydrous oxide surfaces, and (c) borate ion in solution. It occurs as borosilicate to the extent of 20 to 200 ppm in most semi-precious minerals that contain 3 to 4 % boron.
Borosilicate contains varying amounts of iron (Fe), aluminum (Al), manganese (Mn), calcium (Ca), lithium (Li) and sodium (Na). As boron is resistant to weathering, its release from the mineral is slow and, therefore, it cannot meet the need of prolonged and heavy cropping.
Though boron is essential for plants, its requirements and tolerances vary widely from plant to plant. It is required during (a) active cell division, (b) pollen germination, flower formation, fruit and root development, material transportation and cation absorption, (c) new cell development in meristematic tissue, (d) synthesis of amino acids and proteins, (e) nodule formation in legumes, ( f ) translocation of sugars, (g) polymerization of phenolic compounds, and (h) regulation of carbohydrate metabolism. Although boron is required for the growth of agricultural crops, it is not necessary for algae, diatoms, animals, fungi and microorganisms.
Fruits, vegetables, and field crops may suffer from boron deficiency. The first visual symptom is cessation of terminal bud growth, followed by the death of young leaves. Boron deficiency restricts flowering and fruit development, and the symptoms are (a) thickened, wilted or curled leaves, (b) thickened, cracked or water-soaked condition of petioles and stems, and (c) discoloration, cracking or rotting of fruits, tubers or roots. The breakdown of internal root tissues gives rise to darkened areas, referred to as black or brown heart.
The total boron content in soil varies from region to region and soil to soil. In Indian soils, for instance, the total boron content ranges between 4 and 630 mg/kg soil, while the available boron varies from traces to 68 mg/kg soil. Irrigation of arid and semi-arid soils with boron-rich water causes toxicity in plants, which can be reduced with the addition of organic matter.
Boron is available in soils as an organic fraction and is released on decomposition to be partly absorbed by plants and partly lost during leaching. In soil solution, boron is present as a non-ionized molecule (H₃BO₃) which is absorbed by plant roots and distributed with the transpiration stream. The soil texture, pH and the moisture affect the movement of boron in soils. Coarsetextured sandy soils are low in boron and crops in such soils require additional boron in the form of borax, whereas crops in fine-structured sandy soils do not respond to the added boron. Fine-textured soils retain added boron for longer periods than coarse-textured soils. Clays retain boron more effectively than sands. Plant uptake of boron from clayey soils is larger than that from sandy soils.
The soil pH influences the availability of boron; the higher the pH, the lower the boron uptake and the greater the deficiency. Generally, for the same type of crop, the application rate of a fertilizer containing water-soluble boron is lesser for coarse soils than for fine-textured sandy soils. Apple, alfalfa, asparagus, beet, celery, sunflower are some of the crops requiring high levels of boron (more than 0.5 ppm), whereas carrots, cotton, lettuce, peanuts, peach, sweet potato, tobacco and tomato need only 0.10 to 0.15 ppm of boron. The requirement of barley, beans, citrus, corn, forage grasses, soybeans and strawberry is lower than 0.1 ppm of the available soil boron.
Interaction of boron with nutrients plays a vital role in the efficiency of the use of boron. For instance, boron is particularly effective with phosphorus, potassium and micronutrients, whereas its efficiency suffers with sodium, calcium and magnesium. For a good crop, it is essential to have a correct calcium to boron ratio.
Boron compounds that are used to overcome boron deficiency are borax, boric acid, borosilicate glass or frits, calcium borate (Colemanite) and magnesium borate (Boracite). All boron materials used as fertilizers are stable chemicals and create no storage problem. The various methods by which boron is applied to plants are by drilling, broadcasting and spraying.
The presence of boron in a fertilizer has to be clearly stated on the bag.
Borax (Na₂B₄O₇·10H₂O) the most popular boroncontaining fertilizer. For most crops, 15 to 20 kg borax/ha is applied at the time of sowing or transplanting. As boron is readily leached out from the soil and the initial uptake of the plant is large, it is applied as a fused glass to reduce its solubility.
Solubor, a commercial product, is a highly concentrated and completely soluble source of boron (20 %) like borax. It is preferred to borax and is applied as spray or dust directly to the foliage of fruit trees, vegetables and other crops. Colemanite, a naturally occurring calcium borate (Ca₂B₆O₁₁·5H₂O), is less soluble and is also superior to borax.
Boron frits or borosilicate glass containing up to 6 % boron provide boron traces to plants. Borosilicate glass, due to its slow solubility, makes boron available for a longer time than borax. The finely ground form is more effective than the coarse variety.
A dilute solution of boric acid and water is sprayed to be absorbed by the leaves.

Boron (symbol B) is a metallic element closelyresembling silicon. Boron has a specific gravityof 2.31, a melting point of about 2200°C, anda Knoop hardness of 2700 to 3200, equal to aMohs hardness of about 9.3. At 600°C, boronignites and burns with a brilliant green flame.Minute quantities of boron are used in steelsfor case hardening by the nitriding process toform a boron nitride, and in other steels toincrease hardenability, or depth of hardness. Inthese boron steels, as little as 0.003% is beneficial,forming an iron boride, but with largeramounts the steel becomes brittle and susceptibleto hot-short unless it contains titanium orsome other element to stabilize the carbon . Incast iron, boron inhibits graphitization and alsoserves as a deoxidizer. It is added to iron andsteel in the form of ferroboron.
Boron compounds are employed for fluxesand deoxidizing agents in melting metals, andfor making special glasses. Boron, like siliconand carbon, has an immense capacity for formingcompounds, although it has a differentvalence. The boron atom appears to have a lenticularshape, and two boron atoms can make astrong electromagnetic bond, with the boronacting like carbon but with a double ring.

Boron has the atomic number 5 and the symbol B, and is a so-called metalloid. Boron compounds have been known for many centuries and especially used in the production of glass. At the beginning of the nineteenth century, it was recognised that boron is an essential micronutrient for plants. A deficiency of boron can lead to deformation in the vegetable growth such as hollow stems and hearts. Furthermore, the plant growth is reduced and fertility can be affected. In general, boron deficiency leads to qualitative and quantitative reduction in the production of the crop. Boron is typically available to plants as boric acid [B(OH)₂] or borate [B(OH)₄]^-. The exact role of boron in plants is not understood, but there is evidence that it is involved in pectin cross-linking in primary cell walls, which is essential for normal growth and development of higher plants.

Dust is a flammable solid. Store in a cool, dryplace away from incompatible material, sources of heat andignition. Boron powder may decompose on exposure to airand may have to be stored under a nitrogen blanket.

The space lattice of Boron belongs to the tetragonal system with lattice constants a=0.873 nm, c=1.013 nm (c=0.503 nm is also reported). The rhombohedron system is also formed. The rhombohedron is stable near the melting point.
Energy gap: Eg=1.0–1.5 eV
Activation energy : 1.39±0.05 eV
Electron mobility: μe=0.9 cm2 /V s (300 K, 1.8×10¹⁶ cm^-3 )

Boron is ubiquitous in the earth’s crust, and is found in most soil types in the range 2–100 ppm, and the average concentration of soil boron is estimated to be 10–20 ppm. The primary source of boron is the mineral rasorite, also called kernite. While large areas of the world are boron deficient, high concentrations are found in parts of western United States, and throughout China, Brazil, and Russia. The world’s richest deposits of boron are located in a geographic region that stretches from the Mediterranean countries inland to Kazakhstan.