7440-42-8 Usage
Chemical Description
Boron is used in these molecules due to its strong electron-withdrawing characteristic.
Description
Boron is a trivalent, non-metallic element that occurs abundantly in the evaporite ores, borax and ulexite. It is never found as a free element on Earth and exists in many polymorphs. Boron has several forms, with the most common being amorphous boron, a dark powder that is non-reactive to oxygen, water, acids, and alkalis. It is an essential plant micronutrient and has various industrial and agricultural applications.
Uses
Used in Aerospace Industry:
Boron is used as a high-strength, high-modulus, low-density reinforcement for advanced aerospace applications. Boron aluminum has been used for tube-shaped truss members, reinforcing space vehicle structures, and as a fan blade material for turbofan jet engines.
Used in Electronics Industry:
Boron is used as a dopant in silicon transistor chips to facilitate or impede the flow of current over the chip. This property is essential for many electronic devices that depend on doped-silicon semiconductors and transistors.
Used in Glass and Ceramics Industry:
Boron is used to manufacture borosilicate glass, which is highly resistant to thermal shock, and to form enamels that provide a protective coating for steel.
Used in Nuclear Industry:
Boron is used as an excellent neutron absorber in nuclear reactors to prevent a runaway fission reaction. Boron rods control the rate of fission by absorbing excess neutrons.
Used in Metal Production:
Boron is used as an oxygen scavenger and hardening agent for copper and other metals. It is also used as a reinforcing material for composites.
Used in Cosmetics and Personal Care Industry:
Boron finds uses in the cosmetics industry, such as talc powder, and in the production of soaps and adhesives.
Used in Agriculture:
Boron is an essential micronutrient for plants, promoting growth and development. It is typically available to plants as boric acid or borate. Boron deficiency can lead to deformation in vegetable growth and reduced fertility.
Used in Pyrotechnics:
Amorphous boron can produce a green flare, making it useful in pyrotechnic flares.
Used in Medicine:
Boron is used as medication for the relief of symptoms of arthritis.
Used in Cutting and Grinding Tools:
Boron is used in cutting and grinding tools due to its hardness, being 30-40% harder than silicon carbide and almost twice as hard as tungsten carbide.
Used in Insecticides:
Boric acid is used as an environmentally safe insecticide, acting as a stomach poison and affecting the insects' metabolism.
Used in Antimicrobial Applications:
Boric acid is used as an antiseptic for minor burns or cuts and is sometimes used in dressings.
Used in Sports Equipment:
Boron-epoxy composites have been used in tennis, racquetball, squash, and badminton rackets, fishing rods, skis, and golf club shafts for improving strength and stiffness.
Used in Magnetic Applications:
An alloy of boron, iron, and neodymium is used to create a permanent magnet, known as the neodymium magnet, used in magnetic resonance imaging machines, cell phones, and CD and DVD players.
Used in Chemical and Biochemical Laboratories:
Sodium borate is used to make buffers in biochemical and chemical laboratories.
Used in Organic Synthesis and Wood Preservation:
Compounds of boron are used in organic synthesis, in the manufacture of special types of glasses, and as wood preservatives.
Isotopes
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.
Origin of Name
It is named after the Arabic word bawraq, which means “white borax.”
Characteristics
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.
History
Boron compounds have been known
for thousands of years, but Boron was not discovered
until 1808 by Sir Humphry Davy and by Gay-Lussac and
Thenard. The element is not found free in nature, but occurs
as orthoboric acid usually in certain volcanic spring waters
and as borates in borax and colemanite. Ulexite, another boron
mineral, is interesting as it is nature’s own version of “fiber
optics.” Important sources of boron are the ores rasorite (kernite)
and tincal (borax ore). Both of these ores are found in the
Mojave Desert. Tincal is the most important source of boron
from the Mojave. Extensive borax deposits are also found in
Turkey. Boron exists naturally as 19.9% 10B isotope and 80.1%
11B isotope. Ten other isotopes of boron are known. High-purity
crystalline boron may be prepared by the vapor phase reduction
of boron trichloride or tribromide with hydrogen on
4-6 The Elements
electrically heated filaments. The impure, or amorphous, boron,
a brownish-black powder, can be obtained by heating the
trioxide with magnesium powder. Boron of 99.9999% purity
has been produced and is available commercially. Elemental
boron has an energy band gap of 1.50 to 1.56 eV, which is higher
than that of either silicon or germanium. It has interesting
optical characteristics, transmitting portions of the infrared,
and is a poor conductor of electricity at room temperature,
but a good conductor at high temperature. Amorphous boron
is used in pyrotechnic flares to provide a distinctive green color,
and in rockets as an igniter. By far the most commercially
important boron compound in terms of dollar sales is Na2B4O7
· 5H2O. This pentahydrate is used in very large quantities in
the manufacture of insulation fiberglass and sodium perborate
bleach. Boric acid is also an important boron compound
with major markets in textile fiberglass and in cellulose insulation
as a flame retardant. Next in order of importance is borax
(Na2B4O7 · 10H2O) which is used principally in laundry products.
Use of borax as a mild antiseptic is minor in terms of dollars
and tons. Boron compounds are also extensively used in
the manufacture of borosilicate glasses. The isotope boron-10
is used as a control for nuclear reactors, as a shield for nuclear
radiation, and in instruments used for detecting neutrons.
Boron nitride has remarkable properties and can be used to
make a material as hard as diamond. The nitride also behaves
like an electrical insulator but conducts heat like a metal. It also
has lubricating properties similar to graphite. The hydrides are
easily oxidized with considerable energy liberation, and have
been studied for use as rocket fuels. Demand is increasing for
boron filaments, a high-strength, lightweight material chiefly
employed for advanced aerospace structures. Boron is similar
to carbon in that it has a capacity to form stable covalently
bonded molecular networks. Carboranes, metalloboranes,
phosphacarboranes, and other families comprise thousands
of compounds. Crystalline boron (99.5%) costs about $6/g.
Amorphous boron (94–96%) costs about $1.50/g. Elemental
boron and the borates are not considered to be toxic, and they
do not require special care in handling. However, some of the
more exotic boron hydrogen compounds are definitely toxic
and do require care.
Production Methods
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.
Production Methods
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.
Preparation
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.
Hazard
Powdered or fine dust of elemental boron is explosive in air and toxic if inhaled. Several ofthe compounds of boron are very toxic if ingested or if they come in contact with the skin. Thisis particularly true of the boron compounds used for strong insecticides and herbicides.
Health Hazard
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.
Flammability and Explosibility
Nonflammable
Potential Exposure
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.
Shipping
Boron powder or dust: UN3178 Flammable solid,
inorganic, Hazard Class: 4.1; Labels: 4.1—Flammable solid.
Toxicity evaluation
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.
Incompatibilities
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.
Precautions
Elemental boron is non-toxic and common boron compounds, such as borates and boric
acid, have low toxicity (approximately similar to table salt with the lethal dose being
2–3 g/kg) and 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 care when handling
Check Digit Verification of cas no
The CAS Registry Mumber 7440-42-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 4 and 2 respectively.
Calculate Digit Verification of CAS Registry Number 7440-42:
(6*7)+(5*4)+(4*4)+(3*0)+(2*4)+(1*2)=88
88 % 10 = 8
So 7440-42-8 is a valid CAS Registry Number.
InChI:InChI=1/B
7440-42-8Relevant articles and documents
The .BH4 Radical: an Electron Spin Resonance Study of the Radiolysis of NaBH4
Symons, Martyn C. R.,Chen, Tsing,Glidewell, Christopher
, p. 326 - 328 (1983)
Exposure of NaBH4(NaBD4) to 60Co γ-rays at 77 K gave a species having a large proton hyperfine coupling to two equivalent protons (deuterons), and a small coupling to two other protons (deuterons), together with a strongly anisotropic coupling to 11B.
Oxidation Intermediates of Borohydride and Tetraphenylborate Ions in Aqueous Solutions obtained by Pulse Radiolysis
Horii, Hideo,Taniguchi, Setsuo
, p. 915 - 916 (2007/10/02)
Absorption spectra of one-electron oxidized intermediates (the H4B and the Ph4B radicals) were observed upon the oxidation of H4B(1-) and Ph4B(1-) by the azide radical (N3), Br2(1-), or (SCN)2(1-) in pulse-irradiated solutions; the spectra
