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Aluminium sulfate, written as Al2(SO4)3 or Al2O12S3, 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 Al2(SO4)3•16H2O and octadecahydrate Al2(SO4)3•18H2O are the most common.
It can also be very effective as a molluscicide, killing spanish slugs. 
Recent research suggests aluminum sulfate may contribute to dementia and Alzheimer's disease.
Additional recommended knowledge
2Al(OH)3 + 3H2SO4 + 3H2O → Al2(SO4)3·6H2O
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 the active ingredient of some antiperspirants; however, beginning in 2005 the US Food and Drug Administration no longer recognized it as a wetness reducer.
Aluminum Sulfate is usually found in baking powder.
It is also used in styptic pencils, and pain relief from stings and bites; it is the active ingredient in popular pain relief products such as Stingose.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Aluminium_sulfate". A list of authors is available in Wikipedia.|