Borax

Borax is a somewhat generic name used to describe a number of closely related minerals or chemical compounds:

Anhydrous borax (₂₄₇)
Borax pentahydrate (₂₄₇)
Borax decahydrate (₂₄₇)

The borax term is most usually used to describe borax decahydrate.

Its name came from Arabic būraq or bauraq بورق .

Borax, also called sodium borate or sodium tetraborate, is an important boron compound. It is a soft white many-sided crystal that dissolves easily in water. If left exposed to dry air, it slowly loses its water of hydration and becomes the white chalky mineral tincalconite (₂₄₇). Commercially sold borax is usually partially dehydrated.

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 American southwest, the Atacama desert in Chile, and in Tibet. Borax may also be produced synthetically from other boron compounds.

Borax is widely used in detergents, water softeners, soaps, disinfectants, and pesticides. One of its most widely advertised uses was as a hand-cleaner for industrial workers. It is used in making enamel glazes, glass and strengthening pottery and ceramics. It is also easily converted to boric acid or borate, which have many applications. It is also used to make buffer solutions that are used in chemical analysis.

Large amounts of borax pentahydrate are used for manufacturing insulating fibreglass and cellulose insulation as a fire retardant and anti-fungal compound. Large amounts are also used in production of sodium perborate monohydrate for use in detergents.

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.

When used in a mixture, borax can be used to kill carpenter ants and fleas. Borax is also an ingredient in Slime.

The origin of the name is traceable to the Persian word bürah. The word was also used disparagingly in the 1940s to refer to tawdrily designed modernistic furniture and other works of industrial design. Some say that the use came from advertisement displays for the household cleaner, though the use may also derive from the Yiddish word "borachs," meaning rented furniture.

Borax is also a food additive in some countries (it is banned in the United States), with E number E285. Its use is similar to salt, and it appears notably in French and Iranian caviar. Despite its use as an insecticide and reputation as a toxin, the LD50 toxicity of borax is about the same as that of table salt (both are around 3,000 mg/kg body mass).

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