ALUMINIUM SULFATE

Aluminium sulfate
Aluminium sulfate hexadecahydrate
General
Systematic name	Aluminium sulfate hexadecahydrate
Other names	Cake alum Filter alum Papermaker's alum alumogenite Aluminum sulfate Aluminium sulphate
Molecular formula	Al2(SO4)3·16H2O
Molar mass	342.15 g/mol as anhydrous salt
Appearance	white crystalline solid
CAS number	[10043-01-3]
EINECS number	233-135-0
Properties
Density and phase	2.672 g/cm³, solid
Solubility in water	870 g/L
In ethanol	Slightly soluble (anh.) Insoluble (hydrate)
Melting point	770 °C ''decomp.''
Structure
Coordination geometry	?
Crystal structure	monoclinic (hydrate)
'Safety data'
PEL-TWA (OSHA)	—
RTECS number	BD1700000
Supplementary data page
Structure & properties	''n'', ''εr'', etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other cations	Gallium sulfate Magnesium sulfate
Related compounds	''See'' Alum
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

'Aluminium sulfate' is a widely used industrial chemical. It is sometimes incorrectly referred to as 'alum', as it is closely related to this group of compounds. It occurs naturally as the mineral alunogenite. It is frequently used as a flocculating agent in the purification of drinking water and waste water treatment plants, and also in paper manufacturing.
Aluminium sulfate is rarely, if ever, encountered as the anhydrous salt. It forms a number of different hydrates, of which the hexadecahydrate is the most common.
It can also be very effective as a molluscicide, killing spanish slugs.
[1]

Contents

Preparation

Uses

See also

References

External links

Preparation

Aluminium sulfate may be made by dissolving aluminium hydroxide, Al(OH)₃, in sulfuric acid, H₂SO₄:
2Al(OH)₃ + 3H₂SO₄ + 10H₂O → Al₂(SO₄)₃·16H₂O

Uses

Aluminium Sulfate is used in water purification and as a mordant in dyeing and printing textiles. In water purification, it causes impurities to coagulate which are removed as the particulate settles to the bottom of the container or more easily filtered. This process is called coagulation or flocculation.
When dissolved in a large amount of neutral or slightly-alkaline water, aluminium sulfate produces a gelatinous precipitate of aluminium hydroxide, Al(OH)₃. In dyeing and printing cloth, the gelatinous precipitate helps the dye adhere to the clothing fibers by rendering the pigment insoluble.
Aluminium sulfate is sometimes used to reduce the pH of garden soil, as it hydrolyzes to form the aluminium hydroxide precipitate and a dilute sulfuric acid solution.
Aluminium sulfate is the active ingredient of some antiperspirants; however, beginning in 2005 the US Food and Drug Administration no longer recognized it as a wetness reducer.
It is also used in styptic pencils.

See also

★ Camelford, a town in Cornwall (UK) where the local water supplies were accidentally contaminated with aluminium sulfate.

References

★ General Chemistry, Pauling, Linus, , , San Francisco, 1970, ISBN 0-486-65622-5

External links

★ International Chemical Safety Card 1191

★ NIOSH Pocket Guide to Chemical Hazards