Aluminum sodium sulfate

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Structural formula
Aluminum ion  Sodium ion  2Sulfate ion
Surname Aluminum sodium sulfate
other names
  • E  521
  • Soda alum
  • Soda alum
Molecular formula
  • NaAl (SO 4 ) 2 (anhydrous)
  • NaAl (SO 4 ) 2 12 H 2 O (dodecahydrate)
Brief description

colorless solid

External identifiers / databases
CAS number 10102-71-3
EC number 233-277-3
ECHA InfoCard 100.030.239
PubChem 24939
ChemSpider 23313
Wikidata Q413559
Molar mass
  • 242.09 g mol −1 (anhydrous)
  • 458.29 g mol −1 (dodecahydrate)
Physical state



1.61 g cm −3 (dodecahydrate)

Melting point

~ 60 ° C (dodecahydrate)

  • soluble in water (dodecahydrate)
  • practically insoluble in ethanol (dodecahydrate)
safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Aluminum sodium sulphate ( E 521 , sodium alum ) in the form of its dodecahydrate is an alum with the composition NaAl (SO 4 ) 2  · 12 H 2 O, which is used as a firming agent , acidifier and acid regulator .


Of course, aluminum sodium sulfate occurs as undecahydrate in the mineral mendocite NaAl (SO 4 ) 2  · 11 H 2 O.


Aluminum sodium sulfate is a colorless solid and a mixed salt of sulfuric acid , which contains sodium and aluminum as metals .

safety instructions

The salt is irritating to the skin, eyes and mucous membranes and can cause eczema . It is suspected of causing allergic reactions and therefore frequent consumption is not recommended. In addition, it is suspected of causing Alzheimer's disease due to aluminum exposure of the body .

See also

Web links

Individual evidence

  1. Entry on E 521: Aluminum sodium sulphate in the European database for food additives, accessed on June 27, 2020.
  2. Entry on SODIUM ALUM in the CosIng database of the EU Commission, accessed on February 12, 2020.
  3. a b c d e David R. Lide: CRC Handbook of Chemistry and Physics A Ready-reference Book of Chemical and Physical Data . CRC Press, 1995, ISBN 978-0-8493-0595-5 , pp. 83 ( limited preview in Google Book search).
  4. This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  5. List of additives and E numbers. In: Federation for Food Law and Food Science , accessed on March 4, 2017 .
  6. ^ DC Ayres, D. Hellier: Dictionary of Environmentally Important Chemicals , 1998, CRC Press, ISBN 0-7514-0256-7 .
  7. Salzburg Chamber of Labor ( Memento from November 28, 2007 in the Internet Archive ) (PDF; 385 kB).