Aluminium sulfate (chemical formula: Al2(SO4)3) is a widely used industrial reagent and is often confused with alum.Aluminium sulfate is commonly used as a flocculant in the purification of drinking water and sewage treatment equipment, as well as in the paper industry.In natural conditions, aluminum sulfate is rarely found as anhydrous salt.It forms a series of hydrates, of which hexahydrate aluminum sulfate is the most common.Aluminum sulfate is also an effective insecticide against mollusks.

Aluminum sulfate is an odorless, white, or off-white crystalline solid or powder. The compound is made by adding aluminum hydroxide to sulfuric acid. It's hygroscopic, which means it has the ability to absorb and hold water molecules from the surrounding atmosphere.