Alum
Alum refers to a group of chemical compounds, most commonly Potassium Alum (K₂SO₄·Al₂(SO₄)₃·24H₂O) and Ammonium Alum (NH₄Al(SO₄)₂·12H₂O). Below are the general specifications:
1. Physical Properties:
Appearance: White crystalline powder or colorless, transparent crystals
Odor: Odorless
Solubility: Soluble in water, insoluble in alcohol
pH (5% solution): 3.0 - 4.5 (acidic)
Melting Point: ~92-93°C (for hydrated form, loses water and decomposes)
2. Chemical Composition:
Purity: 98% - 99% (varies by application)
Moisture Content: ≤ 1%
Insoluble Matter: ≤ 0.2%
Iron (Fe): ≤ 50 ppm
Heavy Metals (Pb, As, etc.): Within permissible limits (as per industry standards)
3. Types of Alum:
Potassium Alum (Potash Alum) – K₂SO₄·Al₂(SO₄)₃·24H₂O
Commonly used in water purification, cosmetics, and food processing.
Ammonium Alum – NH₄Al(SO₄)₂·12H₂O
Used in tanning, dyeing, and industrial applications.
Sodium Alum – NaAl(SO₄)₂·12H₂O
Used in the paper and textile industries.
Ferric Alum – FeAl(SO₄)₂·12H₂O
Used in water treatment and the paper industry.
Chrome Alum – KCr(SO₄)₂·12H₂O
Used in tanning leather and photography.
4. Applications:
Water Treatment: As a flocculant in water purification.
Cosmetics & Personal Care: In deodorants and aftershave treatments.
Food Industry: Used as a firming agent and preservative (E number: E522).
Paper & Textile Industry: Used for sizing paper and mordant in dyeing.
Medical & Pharmaceuticals: Used as an astringent and antiseptic.
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