Borax

 ( Borates ) 

Molten borax dissolves many metal oxides to form glasses. This property is important for its uses in metallurgy and for the borax bead test of qualitative chemical analysis.

Borax is soluble in a variety of solvents; however, it is notably insoluble in ethanol.

The term borax properly refers to the so-called "decahydrate" , but that name is not consistent with its structure. It is actually octahydrate. The anion is not tetraborate but tetraborate , so the more correct formula should be . However, the term may be applied also to the related compounds. Borax "pentahydrate" has the formula , which is actually a trihydrate . It is a colorless solid with a density of that crystallizes from water solutions above in the rhombohedral crystal system. It occurs naturally as the mineral tinkhanite. It can be obtained by heating the "decahydrate" above . Borax "dihydrate" has the formula , which is actually anhydrous, with the correct formula . It can be obtained by heating the "decahydrate" or "pentahydrate" to above . Anhydrous borax is sodium tetraborate proper, with formula . It can be obtained by heating any hydrate to . It has one amorphous (glassy) form and three crystalline forms – α, β, and γ, with melting points of , and respectively. is the stable form.

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.

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 polymer bed are used to chromatograph non-glycated hemoglobin differentially from glycated hemoglobin (chiefly HbA1c), which is an indicator of long-term hyperglycemia in diabetes mellitus

Borax alone does not have a high affinity for hardness cations, although it has been used for water softening. A general chemical equation for water softening is (R is the dissolved cation, usually calcium or magnesium):

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 ammonium chloride is used as a flux when welding iron and steel. It lowers the melting point of the unwanted iron oxide (Mill scale), allowing it to run off. Borax is also mixed with water as a flux when soldering jewelry such as gold or silver, where it allows the molten solder to Wetting the metal and flow evenly into the joint. Borax is also a flux for "pre-tinning" tungsten with zinc, making the tungsten soft-solderable. Borax is often used as a flux for forge welding.

In Artisanal 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. 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. The method has also been promoted in Bolivia and Tanzania.

A rubbery polymer sometimes called Slime, Flubber, "gluep" or "glurch" (or erroneously called Silly Putty, which is based on silicone polymers), can be made by polyvinyl alcohol with borax. Making flubber from polyvinyl acetate-based glues, such as Elmer's Glue, and borax is a common elementary science demonstration.

Borax, given the E number E285, is used as a food additive but this use is banned in some countries, such as Australia, China, Thailand and the United States. As a consequence, certain foods, such as caviar, produced for sale in the United States contain higher levels of salt to assist preservation. In addition to its use as a preservative, borax imparts a firm, rubbery texture to food. In China, borax (p=péng shā or link=no) has been found in foods including wheat and rice noodles named lamian (link=no), shahe fen (link=no), char kway teow (link=no), and chee cheong fun (link=no) In Indonesia, it is a common, but forbidden, additive to such foods as noodles, bakso (meatballs), and steamed rice.

• Ingredient in vitreous enamel.
• Component of glass, pottery, and .
• Used as an additive in ceramic slips and to improve fit on wet, greenware, and bisque.
• Flame retardant treatment for fabric.
• Fungicide compound for cellulose insulation.
• Mothproofing 10% solution for wool.
• Pulverized for the prevention of stubborn pests (e.g. ) in closets, pipe and cable inlets, wall panelling gaps, and inaccessible locations where ordinary are undesirable.
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• Tackifier ingredient in casein, starch and dextrin-based adhesives.
• To make indelible ink for by dissolving shellac into heated borax.
• Curing agent for snake skins.
• Curing agent for salmon eggs, for use in sport fishing for salmon.
• Swimming pool buffering agent to control pH.
• In nuclear reactors and spent fuel pools as a neutron absorber to control reactivity and to shut down a nuclear chain reaction.
• As a micronutrient fertilizer to correct boron-deficient soils.
• Preservative in taxidermy.
• To color fires with a green tint.
• Traditionally used to coat dry-cured meats such as hams to improve the appearance and discourage flies.
• Used as a flux for melting metals and alloys in casting to draw out impurities and prevent Redox.
• Used as a woodworm treatment (diluted in water).
• 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.

The lethal dose is not necessarily the same for humans; human studies in three borate exposure-rich comparison groups (U.S. Borax mine and production facility workers, Chinese boron workers, Turkish residents living near boron rich regions) produced no indicators of developmental toxicity in blood and semen tests. The highest estimated exposure was 5 mg B/kg/day, likely due to eating in contaminated workplaces, more than 100 times the average daily exposure.

Borax is absorbed poorly through intact skin, although fatalities have been recorded in persistent treatment of rashes and open wounds with boric acid-containing ointments and bath solutions. Borax is readily absorbed orally, well above 90%, and mostly excreted through the urine. Fatal cases attributed to ingestion include small children mistakenly drinking pesticides or suicide attempts with large volumes of crystals. No genotoxicity or carcinogenicity has been recorded in studies.

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.

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." 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.

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 European Union 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 . 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". It was proposed for addition to REACH Annex XIV by the ECHA on July 1, 2015. If this recommendation is approved, all imports and uses of borax in the EU will have to be authorized by the ECHA.

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." 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).

• Borax bead test
• John Veatch
• List of cleaning agents
• Sodium borohydride
• Ulexite

• (fused borax)
• National Pollutant Inventory – Boron and compounds
• NIOSH Pocket Guide to Chemical Hazards
• Sodium Borate in sefsc.noaa.gov