Characteristic

Aluminum sulfate hydrate is a chemical compound with the formula Al₂(SO₄)₃•xH₂O (x≈14-18). It forms a number of different hydrates, of which the hexadecahydrate Al₂(SO₄)₃•16H₂O and octadecahydrate Al₂(SO₄)₃•18H₂O are the most common. The heptadecahydrate, whose formula can be written as [Al(H2O)6]2(SO4)3•5H2O, occurs naturally as the mineral alunogen.

Chemical formula:Al₂(SO₄)₃•xH₂O

Molar mass:666.44 g/mol

Appearance:white crystalline solid;

Density:2.672 g/cm³ (anhydrous);1.62 g/cm³ (octadecahydrate)

Melting point:86.5 °C 

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 is a chemical compound commonly used as a flocculating agent in the purification of drinking water and waste water treatment plants, and also in paper manufacturing. Used as coagulant in decolorization and COD removal of secondary yeast wastewater effluents. It is also plays a significant role in arsenic removal by coagulation process.