Ammonium alum

Ammonium alum (CAS 7784-25-0, EC 232-055-3) is an inorganic double salt of aluminium and ammonium, also referred to as ammonium aluminium alum or ammonia alum sulfate. It carries no E-code designation and is distinct from potassium alum, though both belong to the alum family of sulphate salts.

In water treatment, ammonium alum acts as a coagulant by releasing aluminium ions that neutralise negatively charged suspended particles, causing them to aggregate and settle. In textile and leather processing, it functions as a mordant and tanning auxiliary, fixing dyes to fibres and stabilising collagen structure. Pulp and paper producers use it for rosin sizing, where it precipitates resin onto cellulose fibres to improve water resistance.

Ammonium alum is available in technical and water treatment grades, typically supplied as a white crystalline powder. It falls under REACH registration requirements for EU supply. Packaging commonly ranges from 25 kg bags to bulk quantities depending on application volume and purity specification.