A

Alums

MAl(SO₄)₂·12H₂O
Quick Reference
Formula / NotationMAl(SO₄)₂·12H₂O
Also Known AsDouble sulfate salts, potassium alum (KAl(SO₄)₂·12H₂O), chrome alum, ferric alum

What is Alums?

Alums are a class of double sulfate salts with the general formula XM(SO₄)₂·12H₂O, where X is a monovalent cation and M is a trivalent metal ion. The most common is potassium alum KAl(SO₄)₂·12H₂O, widely used in water purification, food processing, and as an astringent.

Formula & Notation

MAl(SO₄)₂·12H₂O

Other Names / Synonyms: Double sulfate salts, potassium alum (KAl(SO₄)₂·12H₂O), chrome alum, ferric alum

Properties & Characteristics

Alums are double sulfate salts of the general formula M⁺M³⁺(SO₄)₂·12H₂O, where M⁺ is a monovalent cation (K⁺, Na⁺, NH₄⁺) and M³⁺ is a trivalent cation (Al³⁺, Cr³⁺, Fe³⁺). They crystallise in regular octahedral or cubic forms and are highly soluble in water. The most common is potassium alum, KAl(SO₄)₂·12H₂O.

Uses & Applications

Potassium alum is used as a mordant in textile dyeing, as a coagulant in water purification, in food preservation, and in cosmetic astringents. Chrome alum is used in leather tanning. Alums serve as leavening agents in baking powder.

Safety Information

Alums are generally of low toxicity. Large ingested quantities can cause gastrointestinal irritation. Aluminium-containing alums should be used with care in individuals with renal impairment. Avoid inhalation of fine alum dust.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Alums
Formula MAl(SO₄)₂·12H₂O
Synonyms Double sulfate salts, potassium alum (KAl(SO₄)₂·12H₂O), chrome alum, ferric alum

Frequently Asked Questions

Alums are a class of double sulfate salts with the general formula XM(SO₄)₂·12H₂O, where X is a monovalent cation and M is a trivalent metal ion. The most common is potassium alum KAl(SO₄)₂·12H₂O, widely used in water purification, food processing, and as an astringent.

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