ammonia alum
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Definition
Noun: 1. A specific inorganic chemical compound: Ammonia alum is a white, crystalline, water-soluble solid. It is a double sulfate salt containing aluminum and ammonium ions. Its chemical formula is often written as NH₄Al(SO₄)₂·12H₂O.
Usage
- Ammonia alum is primarily used as a mordant in dyeing textiles, helping dyes bind to fabric.
- It is used in water purification and wastewater treatment as a coagulating agent.
- It finds use in leather tanning, papermaking, and as an ingredient in some cosmetics and astringents.
Examples
- "The dyer used ammonia alum to fix the vibrant color to the wool."
- "Ammonia alum is an effective and common coagulant in small-scale water treatment plants."
- "The chemical formula for ammonia alum indicates it contains water of crystallization."
Advanced Usage
- In chemistry, ammonia alum is a member of the broader alum family, which are double sulfate salts with the general formula XAl(SO₄)₂·12H₂O, where X is a monovalent cation like potassium, sodium, or ammonium.
- It is distinguished from potassium alum (potash alum), which is another common type.
Variants and Related Words
- Ammonium alum: A fully synonymous name for the same compound.
- Alum: A general term for a class of double sulfate salts. Ammonia alum is one specific type of alum.
- Potassium alum (Potash alum): A related compound where the ammonium ion is replaced by a potassium ion (KAl(SO₄)₂·12H₂O).
Synonyms
- Ammonium aluminum sulfate
- Aluminum ammonium disulfate dodecahydrate (systematic chemical name)
Notes on Meaning
The term ammonia alum refers specifically to the chemical compound containing ammonium (NH₄⁺) and aluminum (Al³⁺) ions. It should not be confused with other alums (like potassium alum) or with aqueous ammonia (NH₃), which is a different substance entirely.
Noun
- a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum