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Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.029.141 |
| EC Number |
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| E number | E523(acidity regulators, ...) |
| KEGG |
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| RTECS number |
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| UNII |
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| Properties[1] | |
| (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[1] | |
| Hexagonal (anhydrous) Cubic (dodecahydrate) | |
| Octahedral (Al3+) | |
| Hazards[2] | |
| GHS labelling: | |
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| 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Ammonium aluminium sulfate, also known asammonium alum or justalum (though there are many different substances also called "alum"), is a white crystallinedouble 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 mineraltschermigite.[1]
Ammonium alum is made fromaluminium hydroxide,sulfuric acid andammonium sulfate. It forms asolid solution withpotassium alum.Pyrolysis leavesalumina. Such alumina is used in the production of grinding powders and as precursors tosynthetic gems.[3]
Ammonium alum is not a major industrial chemical or a particularly useful laboratory reagent, but it is cheap and effective, which invites many niche applications. It is used in water purification, in vegetable glues, in porcelain cements, indeodorants and in tanning, dyeing and in fireproofing textiles.[4] ThepH of the solution resulting from the topical application of ammonium alum with perspiration is typically in the slightly acid range, from 3 to 5.[5]
Ammonium alum is a common ingredient in animal repellent sprays.[6][7][8]
