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Name Sodium tetraborate decahydrate
Chemical formula Na2B4O7·10H2O
Appearance White solid


Formula weight 381.4 amu
Melting point Decomposes at 348 K (75 °C)
Density 1.7 ×103 kg/m3
Crystal structure ?
Solubility 55 g in 100g water


ΔfH0solid -6289kJ/mol
S0solid 586 J/mol·K


Ingestion GI irritation, large doses may be fatal.
Inhalation May cause irritation.
Skin May cause irritation.
Eyes May cause irritation.
More info Hazardous Chemical Database
SI units were used where possible. Unless otherwise stated, standard conditions were used.

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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 a white chalky substance. Commercially sold borax is usually completely dehydrated.

Borax occurs naturally in evaporite deposits produced by the repeated evaporation of seasonal lakes (see playa). The most commercially important deposits are in 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 strengthing pottery and ceramics. It is also easily converted to boric acid or borate, which have many applications.