Chemical name: Alum

Formula: KAl(SO₄)₂·12H₂O.

Uses:

1. Aluminium-based alums have been used since antiquity, and are still important in many industrial processes.
2. The most widely used alum is potassium alum. It has been used since antiquity as a flocculant to clarify turbid liquids, as a mordant in dyeing, and in tanning.