Borax

The borax (Na₂B₄O₇ 10H₂ Or, boraj, sodium borate or sodium tetraborate) (probably from the Persian word al bürah) it is an important compound of boron. It is the trade name for boron salt. It is a soft white crystal that dissolves in water; with a density (decahydrate) of 1.73 g/cm³. If allowed to settle in the open air, it slowly loses its hydration and becomes tinchalconite (Na₂B₄O₇ •5 H₂O). Commercial borax is usually partially dehydrated.

Natural deposits

Borax occurs naturally in deposits produced by continuous evaporation from stationary lakes. The most important deposits are found near Boron, California, and elsewhere in the southwestern United States, in salt lakes in Bolivia, the Atacama Desert and northern Chile, and Tibet. Borax can also be synthesized from other boron compounds.

Cumulative bórax view in Laguna Colorada, Bolivia.

Uses

Detergents and pesticides

Borax is widely used in detergents, fabric softeners, soaps, disinfectants, and pesticides. In addition, it is often used in the manufacture of slime, enamels, glass and ceramics. It is also easily converted to boric acid or borate, which have many uses.

As a flux

A mixture of borax and ammonium chloride is used as a flux when welding iron and steel. Its function is to lower the melting point of the unwanted iron oxide.

In jewelry

Borax is also used in jewelry mixed with water as a flux when soldering gold, silver, etc. It allows the molten metal to flow evenly over the mold, and preserves the shine and polish of the piece to be welded. It attacks certain types of semi-precious stones, such as the entire family of zircons, which are destroyed on contact with borax and with a high temperature, necessary to melt the metal.

Glass, paint and soldering

It is used in the manufacture of glass, paint components, welding, and wood preservative.

It is also used as a deoxidizer and as an ingredient in foliar fertilizers.

It is also used as an additive in the application of plasters, since it considerably reduces the setting time of the same.

Sale

It is sold in pentahydrate or decahydrate form. For use in ceramics, it is included decahydrated, to form alkaline stoneware glazes and low temperature. Very good for being of low economic value, adding only clay, quartz and kaolin.

Chemical behavior

Borax has an amphoteric behavior in solution, which makes it possible to regulate the pH in aqueous-based solutions and chemical products. The dissolution of both salts in water is slow and also at a relatively low concentration (barely 6%). Borax has the property of dissolving metal oxides when this compound merges with them. It has a better dissolving behavior if the pH is between 12 and 13, and BO₂- salts are formed in an alkaline environment.