Borax
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Names | |
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IUPAC name
disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane;decahydrate[1]
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Other names
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Identifiers | |
3D model (
JSmol ) |
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ChEBI | |
ChEMBL | |
ChemSpider | |
EC Number | |
E number | E285 (preservatives) |
KEGG | |
PubChem CID
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RTECS number
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
Na2B4O5(OH)4·8H2O | |
Molar mass | 381.36 g·mol−1 |
Appearance | White or colorless crystalline solid |
Density | 1.73 g/cm3 (decahydrate, solid)[2] |
Melting point | 743 °C (1,369 °F; 1,016 K) (anhydrous)[2] 75 °C (decahydrate, decomposes)[2] |
Boiling point | 1,575 °C (2,867 °F; 1,848 K) (anhydrous)[2] |
31.7 g/L [2] | |
−85.0·10−6 cm3/mol (anhydrous)[2]: p.4.135 | |
Refractive index (nD)
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n1=1.447, n2=1.469, n3=1.472 (decahydrate)[2]: p.4.139 |
Structure[3] | |
Monoclinic, mS92 , No. 15
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C2/c | |
2/m | |
a = 1.1885 nm, b = 1.0654 nm, c = 1.2206 nm α = 90°, β = 106.623°°, γ = 90°
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Lattice volume (V)
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1.4810 nm3 |
Formula units (Z)
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4 |
Pharmacology | |
S01AX07 (WHO) | |
Hazards | |
GHS labelling: | |
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H360 | |
P201, P308+P313 | |
NFPA 704 (fire diamond) | |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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none[4] |
REL (Recommended)
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TWA 1 mg/m3 (anhydrous and pentahydrate)[4][5] TWA 5 mg/m3 (decahydrate)[6] |
IDLH (Immediate danger) |
N.D.[4] |
Related compounds | |
Other anions
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Sodium aluminate |
Other cations
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Lithium tetraborate
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Related compounds
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Boric acid, sodium perborate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Borax (also referred to as sodium borate, tincal ().
It is a colorless crystalline solid that dissolves in water to make a basic solution.
It is commonly available in powder or granular form and has many industrial and household uses, including as a
The terms tincal and tincar refer to native borax, historically mined from dry lake beds in various parts of Asia.[9]
History
Borax was first discovered in dry lake beds in
Borax first came into common use in the late 19th century when Francis Marion Smith's Pacific Coast Borax Company began to market and popularize a large variety of applications under the 20 Mule Team Borax trademark, named for the method by which borax was originally hauled out of the California and Nevada deserts.[10][11]
Etymology
The English word borax is Latinized: the Middle English form was boras, from Old French boras, bourras. That may have been from Medieval Latin baurach (another English spelling), borac(-/um/em), borax, along with Spanish borrax (> borraj) and Italian borrace, in the 9th century, and from Arabic buraq (بورق) as mentioned for example in kitab al-tabikh of Ibn Sayyar al-Warraq.
The words tincal and tincar were adopted into
Chemistry
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Borax-unit-cell-3D-balls.png/170px-Borax-unit-cell-3D-balls.png)
From the chemical perspective, borax contains the [B4O5(OH)4]2− ion. In this structure, there are two four-coordinate boron centers and two three-coordinate boron centers.
It is a proton conductor at temperatures above 21 °C. Conductivity is maximum along the b-axis.[14]
Borax is also easily converted to boric acid and other borates, which have many applications. Its reaction with hydrochloric acid to form boric acid is:
- Na2B4O7·10H2O + 2 HCl → 4 H3BO3 + 2 NaCl + 5 H2O
Borax is sufficiently stable to find use as a
Molten borax dissolves many metal oxides to form glasses. This property is important for its uses in metallurgy and for the
Borax is soluble in a variety of solvents; however, it is notably insoluble in ethanol.[1]
Organic solvent | Temperature °C (°F) |
Borax % by weight in saturated solution |
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Glycerol 98.5% | 20 (68) | 52.60 |
Glycerol 86.5% | 20 (68) | 47.19 |
Ethylene glycol | 25 (77) | 41.60 |
Diethylene glycol | 25 (77) | 18.60 |
Methanol | 25 (77) | 19.90 |
Aqueous ethanol 46.5% | 15.5 (60) | 2.48 |
Acetone | 25 (77) | 0.60 |
Ethyl acetate | 25 (77) | 0.14 |
Temperature °C (°F) |
Borax % by weight in saturated solution |
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0 (32) | 1.99 |
5 (41) | 2.46 |
10 (50) | 3.09 |
15 (59) | 3.79 |
20 (68) | 4.70 |
25 (77) | 5.80 |
30 (86) | 7.20 |
35 (95) | 9.02 |
40 (104) | 11.22 |
45 (113) | 14.21 |
50 (122) | 17.91 |
55 (131) | 23.22 |
60 (140) | 30.32 |
65 (149) | 33.89 |
70 (158) | 36.94 |
75 (167) | 40.18 |
80 (176) | 44.31 |
85 (185) | 48.52 |
90 (194) | 53.18 |
95 (203) | 58.94 |
100 (212) | 65.63 |
The term borax properly refers to the so-called "decahydrate" Na2B4O7·10H2O, but that name is not consistent with its structure. It is actually octahydrate. The
Natural sources
![](http://upload.wikimedia.org/wikipedia/commons/b/b1/Borax_ball.jpg)
Borax occurs naturally in
Naturally occurring borax (known by the trade name Rasorite–46 in the United States and many other countries) is refined by a process of recrystallization.[20]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Hauling_Borax%2C_Death_Valley%2C_1904.jpg/220px-Hauling_Borax%2C_Death_Valley%2C_1904.jpg)
Uses
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/63/Borax.jpg/170px-Borax.jpg)
Borax is used in pest control solutions because it is toxic to ants. Because it is slow-acting, worker ants will carry the borax to their nests and poison the rest of the colony.[21]
Borax is used in various household laundry and cleaning products,
Borate ions (commonly supplied as boric acid) are used in biochemical and chemical laboratories to make buffers, e.g. for polyacrylamide gel electrophoresis of DNA and RNA, such as TBE buffer (borate buffered tris-hydroxymethylaminomethonium)[26][27] or the newer SB buffer or BBS buffer (borate buffered saline) in coating procedures. Borate buffers (usually at pH 8) are also used as preferential equilibration solutions in dimethyl pimelimidate (DMP) based crosslinking reactions.[citation needed]
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 form complex ions with various substances. Borate and a suitable
Borax alone does not have a high affinity for hardness cations, although it has been used for water-softening. Its chemical equation for water-softening is given below:
The sodium ions introduced do not make water "hard". This method is suitable for removing both temporary and permanent types of hardness.
A mixture of borax and
![](http://upload.wikimedia.org/wikipedia/en/thumb/9/91/Borax_wagons.jpg/220px-Borax_wagons.jpg)
In artisanal gold mining, borax is sometimes used as part of a process known as the borax method (as a flux) meant to eliminate the need for toxic mercury in the gold extraction process, although it cannot directly replace mercury. Borax was reportedly used by gold miners in parts of the Philippines in the 1900s.[30][31] There is evidence that, in addition to reducing the environmental impact, this method achieves better gold recovery for suitable ores and is less expensive. This borax method is used in northern Luzon in the Philippines, but miners have been reluctant to adopt it elsewhere for reasons that are not well understood.[32] The method has also been promoted in Bolivia[33] and Tanzania.[34]
A rubbery polymer sometimes called
Borax, given the
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Boron_mine_pit.jpg/220px-Boron_mine_pit.jpg)
Other uses include:
- Ingredient in enamel glazes[43]
- Component of glass, pottery, and ceramics[44]
- Used as an additive in ceramic slips and bisque[citation needed]
- Fire retardant[45]
- Anti-fungal compound for cellulose insulation[44]
- Mothproofing 10% solution for wool[46]
- Pulverized for the prevention of stubborn pests (e.g. German cockroaches) in closets, pipe and cable inlets, wall panelling gaps, and inaccessible locations where ordinary pesticides are undesirable[47]
- Precursor for sodium perborate monohydrate that is used in detergents, as well as for boric acid and other borates[citation needed]
- Tackifier ingredient in casein, starch and dextrin-based adhesives[48]
- Precursor for boric acid, a tackifier ingredient in polyvinyl acetate, polyvinyl alcohol-based adhesives
- To make indelible ink for dip pens by dissolving shellac into heated borax[citation needed]
- Curing agent for snake skins[citation needed]
- Curing agent for salmon eggs, for use in sport fishing for salmon[49]
- Swimming pool
- Neutron absorber, are used in nuclear reactors and spent fuel pools to control reactivity and to shut down a nuclear chain reaction[51]
- As a micronutrient fertilizer to correct boron-deficient soils[52][53]
- Preservative in taxidermy[54]
- To color fires with a green tint[55]
- Traditionally used to coat dry-cured meats such as hams to improve the appearance and discourage flies[56][57][58]
- Used by blacksmiths in forge welding[29]
- Used as a casting to draw out impurities and prevent oxidation[citation needed]
- Used as a woodworm treatment (diluted in water)[citation needed]
- In particle physics as an additive to nuclear emulsion, to extend the latent image lifetime of charged particle tracks. The first observation of the pion, which was awarded the 1950 Nobel Prize, used this type of emulsion.[59][60]
Toxicity
According to one study, borax is not acutely toxic. Its LD50 (median lethal dose) score is tested at 2.66 g/kg in rats, meaning that a significant dose of the chemical is needed to cause severe symptoms or death. The lethal dose is not necessarily the same for humans. On pesticide information websites it is listed as a non-lethal compound and of no hazardous concerns.
Borax has been in use as an insecticide in the United States with various restrictions since 1946. All restrictions were removed in February 1986 due to the low toxicity of borax, as reported in two EPA documents relating to boric acid and borax.[61][62]
EPA has determined that, because they are of low toxicity and occur naturally, boric acid and its sodium salts should be exempted from the requirement of a tolerance (maximum residue limit) for all raw agricultural commodities.[61]
Although it cited inconclusive data, a re-evaluation in 2006 by the EPA still found that "There were no signs of toxicity observed during the study and no evidence of cytotoxicity to the target organ."[63] In the reevaluation, a study of toxicity due to overexposure was checked and the findings were that "The residential handler inhalation risks due to boric acid and its sodium salts as active ingredients are not a risk concern and do not exceed the level of concern..." but that there could be some risk of irritation to children inhaling it if used as a powder for cleaning rugs.
Overexposure to borax dust can cause respiratory irritation, while no skin irritation is known to exist due to external borax exposure. Ingestion may cause gastrointestinal distress including nausea, persistent vomiting, abdominal pain, and diarrhea. Effects on the vascular system and human brain include headaches and lethargy but are less frequent. In severe cases, a "beefy" red rash affecting the palms, soles, buttocks and scrotum has occurred. [64]
The Indonesian Directorate of Consumer Protection warns of the risk of liver cancer with high consumption of borax over a period of 5–10 years.[58]
Borax was added to the Substance of Very High Concern (SVHC) candidate list on December 16, 2010. The SVHC candidate list is part of the EU Regulations on the Registration, Evaluation, Authorisation and Restriction of Chemicals 2006 (REACH), and the addition was based on the revised classification of borax as toxic for reproduction category 1B under the CLP Regulations. Substances and mixtures imported into the EU which contain borax are now required to be labelled with the warnings "May damage fertility" and "May damage the unborn child".[65] It was proposed for addition to REACH Annex XIV by the ECHA on July 1, 2015.[66] If this recommendation is approved, all imports and uses of borax in the EU will have to be authorized by the ECHA.[needs update]
A review of the boron toxicity (as boric acid and borates) published in 2012 in the Journal of Toxicology and Environmental Health concluded: "It clearly appears that human B [boron] exposures, even in the highest exposed cohorts, are too low to reach the blood (and target tissue) concentrations that would be required to exert adverse effects on reproductive functions."[67] A draft risk assessment released by Health Canada in July 2016 has found that overexposure to boric acid has the potential to cause developmental and reproductive health effects. Since people are already exposed to boric acid naturally through their diets and water, Health Canada advised that exposure from other sources should be reduced as much as possible, especially for children and pregnant women.
The concern is not with any one product, but rather multiple exposures from a variety of sources. With this in mind, the department also announced that certain pesticides that contain boric acid, which are commonly used in homes, will have their registrations cancelled and be phased out of the marketplace. As well, new, more protective label directions are being introduced for other boric acid pesticides that continue to be registered in Canada (for example, enclosed bait stations and spot treatments using gel formulations).[68]
Footnotes
See also
- Borax bead test
- John Veatch
- List of cleaning agents
- Sodium borohydride
- Ulexite
References
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- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0057". National Institute for Occupational Safety and Health (NIOSH).
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- ^ NIOSH Pocket Guide to Chemical Hazards. "#0058". National Institute for Occupational Safety and Health (NIOSH).
- ^ "Potential Commodities NFPA 704" (PDF). Archived from the original (PDF) on May 17, 2016. Retrieved December 9, 2018.
- ^ "CompTox Chemicals Dashboard". comptox.epa.gov. Retrieved January 1, 2022.
- ^ a b "Borax (Na2B4O7·10H2O ) – Sodium Borate – Occurrence, Discovery and Applications". Amoz.com. August 16, 2004.
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- ^ Reiley, Laura (April 22, 2019). "After China turned it into a cheap snack, caviar is at risk of losing its status as a luxury good". The Washington Post. Retrieved April 22, 2019.
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{{cite web}}
: CS1 maint: bot: original URL status unknown (link) - ISBN 978-3-642-01168-9
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External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/38px-Wikisource-logo.svg.png)
- 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