Ammonium alum

Ammonium aluminium sulfate, also known as ammonium alum or just alum (though there are many different substances also called "alum"), is a white crystalline double sulfate usually encountered as the dodecahydrate, formula (NH4)Al(SO4)2·12H2O. It is used in small amounts in a variety of niche applications. The dodecahydrate occurs naturally as the rare mineral tschermigite.

Ammonium alum
Names
Other names
Ammonium alum sulfate
Tschermigite
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.141
EC Number
  • 232-055-3 616-522-2 (dodecahydrate)
E number E523 (acidity regulators, ...)
KEGG
RTECS number
  • WS5640010
UNII
  • InChI=1S/Al.H3N.2H2O4S/c;;2*1-5(2,3)4/h;1H3;2*(H2,1,2,3,4)/q+3;;;/p-3 Y
    Key: LCQXXBOSCBRNNT-UHFFFAOYSA-K Y
  • InChI=1/Al.H3N.2H2O4S/c;;2*1-5(2,3)4/h;1H3;2*(H2,1,2,3,4)/q+3;;;/p-3
    Key: LCQXXBOSCBRNNT-DFZHHIFOAY
  • [Al+3].[O-]S(=O)(=O)[O-].[O-]S([O-])(=O)=O.[NH4+]
Properties
(NH4)Al(SO4)2
Molar mass 237.15 g/mol (anhydrous)
453.33 g/mol (dodecahydrate)
Appearance white crystals
Density 2.45 g/cm3 (anhydrous)
1.64 g/cm3 (dodecahydrate)
Melting point 93.5 °C (200.3 °F; 366.6 K) (dodecahydrate)
Boiling point 120 °C (248 °F; 393 K) dehydr. (dodecahydrate)
15 g/100 ml (20 °C, dodecahydrate)
Structure
Hexagonal (anhydrous)
Cubic (dodecahydrate)
Octahedral (Al3+)
Hazards
GHS labelling:
Warning
H315, H319
P264, P280, P302+P352, P305+P351+P338, P321, P332+P313, P337+P313, P362
Flash point Non-flammable
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references
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