Borax
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225099691
2008-07-11T21:42:46Z
Lucubrations
7461977
moved overly specific material on SB buffer to that topic, keeping a link to that topic.
{{otheruses}}
{{Chembox new
| Name = Borax
| ImageFile = Borax crystals.jpg
| ImageName = Borax crystals
| ImageFile1 = Borax-unit-cell-3D-balls.png
| ImageName1 = Ball-and-stick model of the unit cell of borax decahydrate
| IUPACName = Sodium tetraborate
decahydrate
| Section1 = {{Chembox Identifiers
| CASNo = 1330-43-4 }}
| Section2 = {{Chembox Properties
| Formula = Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>·10H<sub>2</sub>O or Na<sub>2</sub>[B<sub>4</sub>O<sub>5</sub>(OH)<sub>4</sub>]·8H<sub>2</sub>O
| MolarMass = 381.37
| Appearance = white solid
| Density = 1.73 g/cm³ (solid)
| MeltingPt = 741 °C
| BoilingPt = 1575 °C
| pKb = ''see text''
}}
<!--{{Chembox/DeltaHf298|-3276.75}}
{{Chembox/S298|189.53}}
-->
| Section7 = {{Chembox Hazards
| EUClass = not listed
| NFPA-H = 1
| NFPA-F =
| NFPA-R =
| FlashPt = Non-flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Sodium aluminate]]; [[sodium gallate]]
| OtherCations = [[Potassium tetraborate]]
| OtherCpds = [[Boric acid]], [[sodium perborate]]}}
}}
[[Image:Borax wagons.jpg|thumb|right|Old steam tractor and Borax wagons, [[Death Valley]] ]]
'''Borax''' (from Persian ''burah''), also known as '''sodium borate''', '''sodium tetraborate''', or '''disodium tetraborate''', is an important [[boron]] compound, a [[mineral]], and a [[salt (chemistry)|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 [[detergent]]s, [[cosmetic]]s, and [[vitreous enamel|enamel]] glazes.
It is also used to make [[buffer solution]]s in [[biochemistry]], as a [[fire retardant]], as an [[anti-fungal]] compound for [[fiberglass]], as an [[insecticide]], as a [[flux (metallurgy)|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 [[Water of crystallization|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''.<ref>{{cite url | title = Borax, noun | url = http://www.webster.com/dictionary/borax | publisher = Merriam-Webster Online Dictionary | accessdate = 2008-05-01}}</ref><ref>{{cite web | url = http://www.bartleby.com/61/99/B0399900.html | title = Borax | publisher = Bartleby | accessdate = 2008-05-01}}</ref>
== Uses ==
=== Buffer ===
Sodium borate is used in [[biochemistry|biochemical]] and [[chemistry|chemical]] laboratories to make buffers, e.g. for [[gel electrophoresis]] of [[DNA]], such as [[TBE buffer|TBE]] or the newer [[SB buffer]]. Borate buffers (usually at pH 8) are also used as preferential equilibration solution in DMP-based crosslinking reactions.
=== 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 does not 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 (metallurgy)|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]] [[metal]]s 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.<ref>{{citation | first = J.G. | last = Dodd | doi = 10.1119/1.1972398 | journal = Am. J. Phys | volume = 34 | issue = 10 | pages = p. xvi | year = 1966 | title = Soft soldering to tungsten wire | accessdate = 2008-05-01}}</ref>
=== Putty ===
When a borax-water solution is mixed with [[Polyvinyl acetate|PVA glue]] (wood glue) a rubbery precipitate is formed, which is the result of [[Cross-link|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. In consequence certain foods, such as caviar, produced for sale there contain higher levels of [[salt]] to assist preservation.<ref>{{cite web|url=http://www.hanscon.ch/caviar_website/glossary.htm|title= Caviar glossary|work=The Caviar Guide a gourmet review of caviars & fish roe |publisher=Hanson Ltd, Geneva, Switzerland|accessdate=2008-07-07}}</ref>
=== Other uses ===
* Component of [[detergent]]s
* Ingredient in [[vitreous enamel|enamel]] glazes
* Component of [[glass]], [[pottery]], and [[ceramic]]s
* [[Fire retardant]]
* [[Anti-fungal]] compound for [[fibreglass]] and [[cellulose]] insulation
* [[Insecticide]] to kill [[ant]]s and [[flea]]s
* Precursor for [[sodium perborate|sodium perborate monohydrate]] that is used in [[detergent]]s, as well as for [[boric acid]] and other [[borates]]
* Treatment for [[thrush (horse)|thrush]] in [[horse]]s' [[Horse hoof|hooves]]
* Used to make indelible ink for [[dip pen]]s by dissolving [[shellac]] into heated borax
* Curing agent for snake skins
* Swimming pool [[buffering agent]] to control the [[pH]]
== Natural sources ==
[[Image:Borax ball.jpg|left|thumb|150px|Borax "cottonball"]]
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 ==
Borax, sodium tetraborate decahydrate, is not acutely toxic. <ref>http://pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC34355#Toxicity</ref> Its [[LD50]] score is tested at 2.66 g/kg in rats. <ref>http://www2.prosarcorp.com/files_F/doc_0027/32C37.pdf</ref> This does not mean that it is safe, merely that a significant dose of the chemical is needed to cause severe symptoms or death. Simple exposure can cause respiratory and skin irritation. Ingestion may cause gastrointestinal distress including nausea, persistent vomiting, abdominal pain, and diarrhea. Effects on the vascular system and brain include headaches and lethargy, but are less frequent. "''In severe poisonings, a beefy red skin rash affecting palms, soles, buttocks and scrotum has been described. With severe poisoning, erythematous and exfoliative rash, unconsciousness, respiratory depression, and renal failure.''" <ref>http://pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC34355</ref>
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).<ref>[http://www.epa.gov/oppsrrd1/REDs/boric_acid_tred.pdf Report of the Food Quality Protection Act (FQPA) Tolerance Reassessment Eligibility Decision (TRED) for Boric Acid/Sodium Borate Salts<!-- Bot generated title -->]</ref> 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.<ref>''Goodman and Gillman's: The Pharmacological Basis of Therapeutics, 6th edition'', chapter on Antiseptics and Disinfectants, page 971</ref>
== Chemistry ==
[[Image:Tetraborate-xtal-3D-balls.png|left|150px|thumb|The structure of the anion [B<sub>4</sub>O<sub>5</sub>(OH)<sub>4</sub>]<sup>2−</sub> in borax]]
The term ''borax'' is often used for a number of closely related minerals or chemical compounds that differ in their [[Water of crystallization|crystal water]] content:
* Anhydrous borax (Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>)
* Borax pentahydrate (Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>·5H<sub>2</sub>O)
* Borax decahydrate (Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>·10H<sub>2</sub>O)
Borax is generally described as Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>·10H<sub>2</sub>O. However, it is better formulated as Na<sub>2</sub>[B<sub>4</sub>O<sub>5</sub>(OH)<sub>4</sub>]·8H<sub>2</sub>O, since borax contains the [B<sub>4</sub>O<sub>5</sub>(OH)<sub>4</sub>]<sup>2−</sub> ion. In this structure, there are two four-coordinate boron atoms (two BO<sub>4</sub> tetrahedra) and two three-coordinate boron atoms (two BO<sub>3</sub> 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 [[hydrate|water of hydration]] and becomes the white and chalky [[mineral]] [[tincalconite]] (Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>·5H<sub>2</sub>O).
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.
== See also ==
* [[Buffer solution]]
* [[Borax bead test]]
* [[Sodium borohydride]]
* [[Ulexite]]
* [[Twenty-Mule-Team Borax]]
* [[Francis Marion Smith]]
* [[John Veatch]]
== References ==
{{reflist}}
== External links ==
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc05/icsc0567.htm International Chemical Safety Card 0567]
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc12/icsc1229.htm International Chemical Safety Card 1229] (fused borax)
* [http://www.npi.gov.au/database/substance-info/profiles/15.html National Pollutant Inventory - Boron and compounds]
* [http://www.cdc.gov/niosh/npg/npgd0058.html NIOSH Pocket Guide to Chemical Hazards]
* [http://www.sefsc.noaa.gov/HTMLdocs/SodiumBorate.htm Sodium Borate in sefsc.noaa.gov]
[[Category:Borate minerals]]
[[Category:Boron compounds]]
[[Category:Borates]]
[[Category:Cleaning product components]]
[[Category:Cleaning products]]
[[Category:Food additives]]
[[Category:Household chemicals]]
[[Category:Sodium compounds]]
[[Category:Laboratory techniques]]
[[ar:بورق]]
[[bn:বোরাক্স]]
[[bs:Boraks]]
[[ca:Bòrax]]
[[cs:Tetraboritan sodný]]
[[de:Borax]]
[[es:Bórax]]
[[eo:Borakso]]
[[fr:Borax]]
[[gl:Bórax]]
[[id:Bleng]]
[[it:Borace]]
[[lt:Boraksas]]
[[hu:Bórax]]
[[nl:Borax]]
[[ja:ホウ砂]]
[[pl:Boraks rodzimy]]
[[pt:Bórax]]
[[ro:Borax]]
[[sr:Боракс]]
[[sv:Borax]]
[[tr:Boraks]]
[[vi:Borac]]
[[uk:Бура]]
[[zh:硼砂]]