Sodium sulfate (Na2SO4), inorganic compound, also known as mirabilite, white, odorless, bitter crystal or powder, has hygroscopicity. The shape is colorless, transparent, large crystals or small granular crystals. Mainly used in water glass, glass, enamel, pulp, refrigerant mixtures, detergents, desiccants, dye diluents, analytical chemicals, pharmaceuticals and so on.
Potassium aluminium sulfate, commonly known as alum. Molecular formula KAl (SO4) 2. 12H 2O, colorless crystals or powders. No odor, slightly sweet and astringent, convergent. Weathering loses crystalline water in dry air and melting dripping water in moist air. Soluble in glycerol, soluble in water, acidic reaction in aqueous solution, after hydrolysis, there is aluminium hydroxide colloidal precipitation. It is insoluble in alcohol and acetone. Melting point 92.5 C. 9 molecule water was lost when sulfuric acid was dried at 60-65 (?) C, and 12 crystalline water was completely lost at 200 (?) C. Sulfur trioxide was decomposed at higher temperature. Alum has a strong adsorption capacity. It can absorb suspended impurities in water and form precipitation to clarify the water. Therefore, alum is a better water purifier. Alum can be prepared by calcining, extracting and crystallizing alunite.