Borax


Borax and tincar ) is a salt normally encountered as a hydrated borate of sodium, with the chemical formula. Borax mineral is a crystalline borate mineral that occurs in only a few places worldwide in quantities that enable it to be mined economically.
Borax can be dehydrated by heating into other forms with less water of hydration. The anhydrous form of borax can also be obtained from the decahydrate or other hydrates by heating and then grinding the resulting glasslike solid into a powder. It is a white crystalline solid that dissolves in water to make a basic solution due to the tetraborate anion.
Borax is commonly available in powder or granular form and has many industrial and household uses, including as a pesticide, as a metal soldering flux, as a component of glass, enamel, and pottery glazes, for tanning of skins and hides, for artificial aging of wood, as a preservative against wood fungus, as a food additive, and as a pharmaceutic alkalizer. In chemical laboratories it is used as a buffering agent.
The terms tincal and tincar refer to the naturally occurring borax historically mined from dry lake beds in various parts of Asia.

History

Borax was first discovered in dry lake beds in Tibet. Native tincal from Tibet, Persia, and other parts of Asia was traded via the Silk Road to the Arabian Peninsula in the 8th century AD.
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.

Etymology

The English word borax and its previous Middle form boras is a Latinate loan from Old French boras ~ bourras which may have been from Medieval Latin baurach, borac, borax, along with Spanish borrax and Italian borrace, in the 9th century, and from Arabic بورق ~ ~ which is attested in Ibn Sayyar al-Warraq's Kitāb al-Ṭabīkh among many examples, from Middle Persian bwlk', which yielded Persian بوره bure.
The words tincal and tincar were adopted into English in the 17th century from Malay tingkal and from Urdu/Persian/Arabic ; thus the two forms in English. These all appear to be related to the Sanskrit टांकण.

Chemistry

From a chemical perspective, borax contains the 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. Conductivity is maximum along the b-axis.
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:
Borax is sufficiently stable to find use as a primary standard for acid-base titrimetry.
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.
Organic solventTemperature
°C 		Borax % by weight
in saturated solution
Glycerol 98.5%20 52.60
Glycerol 86.5%20 47.19
Ethylene glycol25 41.60
Diethylene glycol25 18.60
Methanol25 19.90
Aqueous ethanol 46.5%15.5 2.48
Acetone25 0.60
Ethyl acetate25 0.14

Temperature
°C 		Borax % by weight in saturated solution
0 1.99
5 2.46
10 3.09
15 3.79
20 4.70
25 5.80
30 7.20
35 9.02
40 11.22
45 14.21
50 17.91
55 23.22
60 30.32
65 33.89
70 36.94
75 40.18
80 44.31
85 48.52
90 53.18
95 58.94
100 65.63

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 tetrahydroxy 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 form and three crystalline forms – α, β, and γ, with melting points of, and respectively. is the stable form.

Natural sources

Borax occurs naturally in evaporite deposits produced by the repeated evaporation of seasonal lakes. The most commercially important deposits are found in: Boron, California; and Searles Lake, California. Also, borax has been found at many other locations in the Southwestern United States, the Atacama Desert in Chile, newly discovered deposits in Bolivia, and in Tibet and Romania. Borax can also be produced synthetically from other boron compounds.
Naturally occurring borax is refined by a process of recrystallization.

Uses

Borax is used in pest control solutions because it is toxic to ants and rats. Because it is slow-acting, worker ants will carry the borax to their nests and poison the rest of the colony. Borax is more effective than zinc borate for termite control but a 1997 paper concluded that exposing at least 10% of the total colony population was needed for effective treatment. In Japan the practice of laying newspapers treated with o-boric acid and borax under buildings has been effective in controlling Coptotermes formosanus and Reticulitermes speratus populations. Decaying wood treated with 0.25 to 0.5 percent DOT was also found to be effective for baiting Heterotermes aureus populations. The paper concluded: "Borate baits would undoubtably be helpful in the long-term, but do not appear sufficient as a sole method of structural protection."
Borax is used in various household laundry and cleaning products, including the 20 Mule Team Borax laundry booster, Boraxo powdered hand soap, and some tooth bleaching formulas.
Borate ions are used in biochemical and chemical laboratories to make buffers, e.g. for polyacrylamide gel electrophoresis of DNA and RNA, such as TBE buffer or the newer SB buffer or BBS buffer in coating procedures. Borate buffers are also used as preferential equilibration solutions in dimethyl pimelimidate based crosslinking reactions.
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, 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 :
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, allowing it to run off. Borax is also mixed with water as a flux when soldering jewelry metals such as gold or silver, where it allows the molten solder to wet 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.
File:Borax wagons.jpg|thumb|Old steam tractor with borax wagons, Death Valley National Park
In artisanal gold mining, borax is sometimes used as part of a process known as the borax method 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", can be made by cross-linking 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 has been found in foods including wheat and rice noodles named lamian, shahe fen, char kway teow, and chee cheong fun. In Indonesia, it is a common, but forbidden, additive to such foods as noodles, bakso, and steamed rice.