Aluminum ammonium sulfate

Ammonium alum recrystallized from water

Description

A white crystalline powder that is also called ammonium alum. Aluminum ammonium sulfate occurs naturally as the mineral tschermigite. It is also one of the many numerous double aluminum sulfate salts that a generically called Alum. These alums have been used in baking powders, dyeing textiles, tanning leathers, and as a substrate for lake pigments. Ammonia alum is also used in developing baths for black and white photographs.

Synonyms and Related Terms

ammonium alum; ammonium aluminum sulfate; alum NF; aluminum ammonium sulphate (Br.); tschermigite

Risks

• Skin contact may cause allergies
• Will corrode steel
• ThermoFisher: SDS

Physical and Chemical Properties

• Composition = AlNH4(SO4)2-12H2O
• Mohs Hardness = 1.5-2.0
• Melting Point = 94.5 C
• Density = 1.645 g/ml
• Soluble in water, glycerol. Insoluble in ethanol.
• Crystals are fibrous and deliquescent

Resources and Citations

• Web Minerals: Tschermigite
• G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 33
• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
• Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
• John and Margaret Cannon, Dye Plants and Dyeing, Herbert Press, London, 1994
• The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 335
• Wikipedia: Ammonium alum Accessed March 2025