Aluminium Sulfate Octahydrate
Other Names: Aluminium sulphate, Dialuminium trisulfate, Cake alum
CAS Number: 10043-01-3
EC Number: 233-135-0
Chemical Formula: Al₂(SO₄)₃·8H₂O
Molar Mass: 666.42 g/mol
Appearance: White to off-white crystalline solid
Aluminium sulfate octahydrate is an inorganic salt composed of aluminium, sulfur, and oxygen, typically used as a coagulating agent. It is commonly applied in water treatment, paper production, and as a mordant in dyeing processes. The octahydrate form contains eight molecules of water of crystallization, making it stable under normal storage conditions.
Chemical and Physical Properties
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Density: ~1.61 g/cm³
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Melting Point: Decomposes before melting
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Solubility in Water: Highly soluble (at ~31.2 g/100 mL at 20°C)
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Solubility in Other Solvents: Insoluble in alcohol and organic solvents
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Odor: Odorless
Applications
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Water and Wastewater Treatment: Used to remove suspended solids and control water pH by coagulation.
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Pulp and Paper Industry: Aids in paper sizing to improve ink absorbency.
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Textile Industry: Employed as a mordant in dyeing processes.
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Construction: Occasionally used in waterproofing and accelerating concrete setting.
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Analytical Chemistry: Applied in laboratory tests as a source of aluminium ions.
Safety

Signal Word: Warning
H290 (41.1%): May be corrosive to metals [Warning Corrosive to Metals]
H318 (91.5%): Causes serious eye damage [Danger Serious eye damage/eye irritation]
P234, P264+P265, P280, P305+P354+P338, P317, P390, and P406
Handling and Storage
Store in a cool, dry, and well-ventilated area in a tightly sealed container. Protect from moisture. Avoid contact with strong acids and bases. Use appropriate personal protective equipment when handling.
