Everything about Sodium Borate totally explained
| Section2 =
| Section7 =
| Section8 =
}}
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 or the Middle Persian
burak.
Uses
Buffer
Sodium borate is used in
biochemical and
chemical laboratories to make
SB buffers, for example 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. However, lithium borate is much more expensive.
Co-complexing
Borax as a source of borate has been used to take advantage of the co-complexing ability of borate with other agents in water to
complex various substances. Borate and a suitable
polymer bed are used to
chromatograph non-
glycosylated hemoglobin differentially from non-enzymatically glycosylated hemoglobin (chiefly
HbA1c), which is a model for long term damage done by
hyperglycemia in
diabetes mellitus. Borate and a proprietary synthetic
amino acid, Deselex (from
Henkel) have been used to complex water "hardness" cations to make a
non-precipitating water "softener". Borate alone doesn't have a high affinity for "hardness" cations, although it has been used for that purpose.
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.
Putty
When a borax-water solution is mixed with
PVA glue (wood glue) a rubbery precipitate is formed, which is the result of
cross-linking in the
polymer.
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 common table salt, and it appears in French and Iranian
caviar.
Other uses
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 grams in humans . The estimated lethal dose (ingested) for adults is 15-20 grams; less than 5 grams can kill a child or pet. 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). 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's 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 isn't 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.
Further Information
Get more info on 'Sodium Borate'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://borax.totallyexplained.com">Borax Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
