Ammonium alum

Ammonium alum (CAS 7784-26-1) is an inorganic double salt of aluminium sulphate and ammonium sulphate, commercially known as ammonia alum or alum ammonium dodecahydrate. It carries no E-number designation and is distinct from potassium alum, though both fall under the broader alum category.

In water treatment, ammonium alum acts as a coagulant by releasing aluminium ions that destabilise suspended particles, enabling flocculation and sedimentation. In leather tanning and textile processing, it functions as a mordant and pH buffer, fixing dyes to fibres and controlling bath acidity. Personal care formulators use it as an astringent and mild preservation agent.

Ammonium alum is available in technical and food-grade forms, supplied as crystalline solid or milled powder. It is subject to REACH registration and can be sourced to FCC specifications where food-contact applications require it. Standard packaging includes 25 kg bags and bulk options for industrial volumes.