Aluminum Sulfate Formula Formula: Al2(SO4)3 Molar mass: 342.15 g/mol IUPAC ID: Aluminum sulfate Melting point: 770 C Density: 2.67 g/cm Soluble in: Water Aluminum Sulfate Classification: Alum compounds Industrial sulfonic acid. Laboratory sulfonic acid. Molecular formula: .HSO3R Purity: sulfonic acid Appearance: pale gray powder