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BORAX

Borax (from Persian burah), also known as sodium
borate, sodium tetraborate, or disodium tetraborate,
is an important boron compound, a mineral, and a salt
of boric acid. It is usually a white powder consisting
of soft colorless crystals that dissolve easily in
water.

Borax has a wide variety of uses. It is a component of
many detergents, cosmetics, and enamel glazes. It is
also used to make buffer solutions in biochemistry, as
a fire retardant, as an anti-fungal compound for
fiberglass, as an insecticide, as a flux in
metallurgy, and as a precursor for other boron
compounds.

The term borax is used for a number of closely related
minerals or chemical compounds that differ in their
crystal water content, but usually refers to the
decahydrate. Commercially sold borax is usually
partially dehydrated.

Name

The origin of the name is traceable to the Medieval
Latin borat, which comes from the Arabic buraq, which
comes from either the Persian burah [1] or the Middle
Persian burak [2]

Uses

Buffer

Sodium borate is used in biochemical and chemical
laboratories to make SB buffers, e.g. for gel
electrophoresis of DNA. It has a lower conductivity,
produces sharper bands, and can be run at higher
speeds than can gels made from TBE buffer or TAE
buffer (5 – 35 V/cm as compared to 5 – 10 V/cm). At a
given voltage, the heat generation and thus the gel
temperature is much lower than with TBE or TAE
buffers, therefore the voltage can be increased to
speed up electrophoresis so that a gel run takes only
a fraction of the usual time. Downstream applications,
such as isolation of DNA from a gel slice or southern
blot analysis, work as expected with sodium borate
gels. Borate buffers (usually at pH 8) are also used
as preferential equilibration solution in DMP-based
crosslinking reactions.

Lithium borate is similar to sodium borate and has all
of its advantages, but permits use of even higher
voltages due to the lower conductivity of lithium ions
as compared to sodium ions.[1] However, lithium borate
is much more expensive.

Flux

A mixture of borax and ammonium chloride is used as a
flux when welding iron and steel. It lowers the
melting point of the unwanted iron oxide (scale),
allowing it to run off. Borax is also used mixed with
water as a flux when soldering jewelry metals such as
gold or silver. It allows the molten solder to flow
evenly over the joint in question. Borax is also a
good flux for 'pre-tinning' tungsten with zinc –
making the tungsten soft-solderable.[2]

Food additive

Borax is used as a food additive in some countries
with the E number E285, but is banned in the United
States. Its use is similar to salt, and it appears in
French and Iranian caviar.

Other uses

Component of detergents
Ingredient in enamel glazes
Component of glass, pottery, and ceramics
Fire retardant
Anti-fungal compound for fibreglass and cellulose
insulation
Insecticide to kill ants and fleas
Precursor for sodium perborate monohydrate that is
used in detergents, as well as for boric acid and
other borates
Treatment for thrush in horses' hooves
Used to make indelible ink for dip pens by dissolving
shellac into heated borax
Curing agent for snake skins

Natural sources
Borax occurs naturally in evaporite deposits produced
by the repeated evaporation of seasonal lakes (see
playa). The most commercially important deposits are
found in Turkey and near Boron, California and other
locations in the Southwestern United States, the
Atacama desert in Chile, and in Tibet. Borax can also
be produced synthetically from other boron compounds.

Toxicity

Boric acid, sodium borate, and sodium perborate are
estimated to have a lethal dose (LD50) from 5 to 20
g/kg in humans[verification needed][3]. These
substances are toxic to all cells, and have a slow
excretion rate through the kidneys. Kidney toxicity is
the greatest, with liver fatty degeneration, cerebral
edema, and gastroenteritis. A reassessment of boric
acid/borax by the United States Environmental
Protection Agency Office of Pesticide Programs found
potential developmental toxicity (especially effects
on the testes).[4] Boric acid solutions used as an eye
wash or on abraded skin are known to be especially
toxic to infants, especially after repeated use
because of its slow elimination rate.

Chemistry
The term borax is often used for a number of closely
related minerals or chemical compounds that differ in
their crystal water content:
Anhydrous borax (Na2B4O7)
Borax pentahydrate (Na2B4O7·5H2O)
Borax decahydrate (Na2B4O7·10H2O)

Borax is generally described as Na2B4O7·10H2O.
However, it is better formulated as
Na2[B4O5(OH)4]·8H2O, since borax contains the
[B4O5(OH)4]2− ion. In this structure, there are two
four-coordinate boron atoms (two BO4 tetrahedra) and
two three-coordinate boron atoms (two BO3 triangles).

Borax is also easily converted to boric acid and other
borates, which have many applications. If left exposed
to dry air, it slowly loses its water of hydration and
becomes the white and chalky mineral tincalconite
(Na2B4O7·5H2O).

When borax is added to a flame, it produces a bright
orange color. This property has been tried in amateur
fireworks, but borax in this use is not popular
because its waters of hydration inhibit combustion of
compositions and make it an inferior source of the
sodium which is responsible for most of its flame
color, and which overwhelms the green contributed to
the flame by boron.

However, commercially available borax can be mixed
with flammables such as methanol to give the
characteristic green flame of boron when ignited,
which then slowly gives way to the characteristic
yellow-orange flame of the sodium.

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April 14, 2008 - Posted by | Uncategorized

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