Borax

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It has been suggested that Sodium boric acid be merged into this article or section. (Discuss)

For other uses, see Borax (disambiguation).

Borax
Image:Borax crystals.jpg
General
Systematic name	Sodium tetraborate decahydrate
Molecular formula	Na₂B₄O₇·10H₂O
Molar mass	381.37 g/mol
Appearance	white solid
CAS number	[1303-96-4]
Properties
Density and phase	1.73 g/cm³, solid
Solubility in water	5.1 g/100 ml (20 °C)
Melting point	75 °C
Boiling point	320 °C
Basicity (pK_b)	see text
Structure
Coordination geometry	?
Crystal structure	Monoclinic
Thermodynamic data
Std enthalpy of formation Δ_fH^o₂₉₈	−3276.75 kJ/mol
Standard molar entropy S^o₂₉₈	189.53 J·K⁻¹·mol⁻¹
Hazards
MSDS	External MSDS
EU classification	not listed
NFPA 704	Image:NFPA 704.svg 0 1 0
Flash point	non-flammable
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Sodium aluminate Sodium gallate
Other cations	Potassium tetraborate
Related compounds	Boric acid Sodium perborate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

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

Anhydrous borax (Na₂B₄O₇)
Borax pentahydrate (Na₂B₄O₇·5H₂O)
Borax decahydrate (Na₂B₄O₇·10H₂O)

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

1 General information
2 Name origin
3 Structure
4 See also
5 External links

[edit] General information

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 (Na₂B₄O₇ · 5H₂O). 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.

Image:Reagan Boraxo.jpg

Borax is widely used in detergents, water softeners, soaps, disinfectants, and pesticides. Its use in detergents is due to its ability to bind to and solvate dirt particles in addition to producing peroxides which have a bleaching effect. 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.

[edit] Name origin

The origin of the name is traceable to the Persian word bürah (also spelled būraq or bauraq بورق ) which in turn comes from Middle Persian burag [1]. The word was also used disparagingly in the 1940s to refer to tawdry 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.

Boric acid, Sodium Borate, and Sodium Perborate are estimated to have a fatal dose from 0.1 to 0.5g/kg (Handbook of Poisoning, Robert H. Dreisback,eight edition,p.314). 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. Boric acid solutions used as an eye wash or abraded skin is known to be especially toxic to infants, especially after repeated use due to its slow elimination rate(Goodman and Gillman's: The Pharmacological Basis of Therapeutics, 6th edition,chapter on Antiseptics and Disinfectants, page 971).

[edit] Structure

Image:Tetraborate-ion-3D-vdW.png

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−</sub> ion. In this structure, there are two four-coordinate boron atoms (two BO₄ tetrahedra) and two three-coordinate boron atoms (two BO₃ triangles).}