Borax, (Na₂B₄O₇·10H₂O, sodium borate or sodium tetraborate) is an important boron compound. It is a soft white many-sided crystal that dissolves easily in water. If left exposed to dry air, it slowly loses its water of hydration and becomes the white chalky mineral tincalconite (Na₂B₄O₇·5H₂O). Commercially sold borax is usually partially dehydrated.

Borax occurs naturally in evaporite deposits produced by the repeated evaporation of seasonal lakes (see playa). The most commercially important deposits are found near Boron, California and other locations in the American southwest, the Atacama desert in Chile, and in Tibet. Borax may also be produced synthetically from other boron compounds.

Borax is widely used in detergents, water softeners, soaps, disinfectants, and pesticides. It is used in making enamel glazes, glass and strengthening pottery and ceramics. It is also easily converted to boric acid or borate, which have many applications.

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 (scale), allowing it to run off.

See also

• John Veatch

• Slime Includes a recipe for homemade slime which uses borax