ammonium alum

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ammonium alum (Wikipedia)
Ammonium aluminium sulfate
Ammonium aluminium sulfate dodecahydrate.svg
IUPAC name
Aluminium ammonium bis(sulfate)[citation needed]
Other names
Ammonium alum
3D model (Jmol)
ECHA InfoCard 100.029.141
EC Number 232-055-3
E number E523 (acidity regulators, ...)
RTECS number WS5640010
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)
Hexagonal (anhydrous)
Cubic (dodecahydrate)
Octahedral (Al3+)
Safety data sheet External MSDS
GHS pictograms Skin Irrit. 2; Eye Irrit. 2
GHS signal word WARNING
H315, H319
P264, P280, P302+352, P305+351+338, P321, P332+313, P337+313, P362
Flash point Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Ammonium aluminium sulfate, also known as ammonium alum or just 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.