sodium perborate

Sodium perborate
Other names	PBS-1 (mono), PBS-4 (tetra)
Identifiers
CAS number	7632-04-4 Y, 10332-33-9 (monohydrate), 10486-00-7 (tetrahydrate)
UN number	1479
RTECS number	SC7350000
Properties
Molecular formula	NaBO3·nH2O
Molar mass	99.815 g/mol (monohydrate); 153.86 g/mol (tetrahydrate)
Appearance	white powders
Hazards
MSDS	ICSC 1046
NFPA 704	1 1 0
Flash point	non-flammable
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium perborate (PBS) is a white, odorless, water-soluble chemical compound with chemical formula NaBO₃. It crystallizes as the monohydrate, NaBO₃·H₂O, tetrahydrate, NaBO₃·4H₂O and trihydrate, NaBO₃·3H₂O. ^[1]The monohydrate and tetrahydrate are the commercially important forms.^[1]

Preparation and chemistry

Sodium perborate is manufactured by reaction of disodium tetraborate pentahydrate, hydrogen peroxide, and sodium hydroxide.^[1]The monohydrate form dissolves better than the tetrahydrate and has higher heat stability; it is prepared by heating the tetrahydrate.^[1] Sodium perborate undergoes hydrolysis in contact with water, producing hydrogen peroxide and borate.^[1]

Structure

Unlike sodium percarbonate and perphosphate, the sodium perborate is not simply addition compounds of hydrogen peroxide, but contains a cyclic anion (B₂O₄(OH)₄^2-) with two peroxo bridges and does not contain the BO₃⁻ ion. ^[2] This makes the substance more stable, and safer for handling and storage. The formulae of the mono and tetra hydrates can therefore be written as Na₂H₄B₂O₈ (anhydrous) and Na₂H₄B₂O₈·6H₂O respectively.^[1]

Uses

It serves as a source of active oxygen in many detergents, laundry detergents, cleaning products, and laundry bleaches.^[1] It is also present in some tooth bleaching formulas. It is used as a bleaching agent for internal bleaching of a non vital root treated tooth. The sodium perborate is placed inside the tooth and left in place for an extended period of time to allow it to diffuse into the tooth and bleach stains from the inside out. It has antiseptic properties and can act as a disinfectant. It is also used as a "disappearing" preservative in some brands of eye drops.

Sodium perborate is a less aggressive bleach than sodium hypochlorite, causing less degradation to dyes and textiles. Borates also have some non-oxidative bleaching properties.

Sodium perborate releases oxygen rapidly at temperatures over 60°C. To make it active at lower temperatures (40-60 °C), it has to be mixed with a suitable activator, typically tetraacetylethylenediamine (TAED).

Hazards

Sodium perborate is an irritant for the skin.

See also

• Amosan
• Sodium percarbonate
• Sodium perphosphate
• Persil

References

1. ^ ^{a b c d e f g} B.J Brotherton Boron: Inorganic Chemistry Encyclopedia of Inorganic Chemistry (1994) Ed. R. Bruce King, John Wiley & Sons ISBN 0471936200
2. ^ Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0-7506-3365-4 

External links

• Borax Detergent Book: Bleaching
• National Pollutant Inventory - Boron and compounds
• Sodium perborate history, image
• Sodium perborate in organic synthesis