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Sodium boric acid be merged into this article or section. (Discuss)
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For other uses, see Borax (disambiguation).
| Borax |
|
| 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 (pKb) |
see text |
| Structure |
Coordination
geometry |
? |
| Crystal structure |
Monoclinic |
| Thermodynamic data |
Std enthalpy of
formation ΔfHo298 |
−3276.75 kJ/mol |
Standard molar
entropy So298 |
189.53 J·K−1·mol−1 |
| Hazards |
| MSDS |
External MSDS |
| EU classification |
not listed |
| NFPA 704 |
|
| Flash point |
non-flammable |
| Supplementary data page |
Structure and
properties |
n, εr, 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.
The name comes from Arabic būraq or bauraq بورق which in turn comes from Middle Persian Burag[1].
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.
Ronald Reagan advertising borax
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.
The origin of the name is traceable to the Persian word bürah. 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).
Structure
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).
See also
- Sodium borohydride
- Sodium boric acid
- Ulexite
- Twenty-Mule-Team Borax
- Francis Marion Smith
- John Veatch
External links
- International Chemical Safety Card 0567
- International Chemical Safety Card 1229 (fused borax)
- National Pollutant Inventory - Boron and compounds
- NIOSH Pocket Guide to Chemical Hazards
- Sodium Borate in sefsc.noaa.gov
- Link page to external chemical sources.
Categories: Articles to be merged since September 2006 | Borate minerals | Borates | Cleaning product components | Cleaning products | Food additives | Household chemicals | Sodium compounds
