Aluminium ammonium sulphate, also known as ammonium alum, is a white crystalline compound with the chemical formula (NH4)Al(SO4)2·12H2O. It is a double salt composed of ammonium sulphate and aluminium sulphate.

This compound is commonly used as a mordant in dyeing and printing textiles, as well as in water purification, papermaking, and as a food additive. It is also used in the manufacture of alumina, which is used to make aluminium metal.

The 500g description simply refers to the quantity of the compound being sold, which is 500 grams. It is important to handle this chemical with care, as it can be an irritant to the skin, eyes, and respiratory system if not properly handled.

Melting point: 93°C (199°F) (decomposes) Density: 1.69 g/cm3 pH: 3.0 – 4.5 (1% aqueous solution) Stability: Stable under normal conditions of use and storage Storage: Store in a cool, dry place away from incompatible materials and sources of heat and ignition. Hazards: Irritant to skin, eyes, and respiratory system. May cause allergic reactions in some people. May be harmful if ingested or inhaled.