Characteristic

Aluminium sulfate is a chemical compound with the formula Al₂(SO₄)₃. It is soluble in water and is mainly used as a coagulating agent (promoting particle collision by neutralizing charge) in the purification of drinking waterand waste water treatment plants, and also in paper manufacturing.

Chemical formula：Al₂(SO₄)₃

Molar mass：342.15 g/mol 

Appearance：white crystalline solid; hygroscopic

Density：2.672 g/cm³ (anhydrous)

Melting point：770 °C (1,420 °F; 1,040 K) 

Solubility in water：31.2 g/100 mL (0 °C);36.4 g/100 mL (20 °C);89.0 g/100 mL (100 °C)

Solubility：slightly soluble in alcohol, dilute mineral acids

Acidity (pKa)：3.3-3.6

Magnetic susceptibility (χ)：-93.0·10−6 cm³/mol

Refractive index (nD)：1.47

Crystal structure：monoclinic (hydrate)

Application

Aluminum sulfate acts as a flocculating agent in the purification of drinking water, and in waste water treatment plants. It acts as a mordant in dyeing, printing, textiles and also used in paper manufacturing. It is a waterproofing agent and accelerator in concrete. Further, it is used as a foaming agent in fire fighting foam, photographic film and in photochemicals. It is also used in styptic pencils, pain relief and in dentistry for gingival retraction cords.