Sodium sulfate is an important chemical raw material. It is the main raw material for the production of sodium sulfide, sodium silicate and other chemical products. It can also be used as a filler for synthetic detergent and a cooking agent for the manufacture of sulfate pulp in the paper industry. Sodium sulfate is also called sodium sulfate, anhydrous mirabilite and anhydrous tannite. White monoclinic fine crystal or powder. The relative density is 2.68 and the melting point is 884 ℃. Soluble in water, the aqueous solution is neutral. Soluble in glycerine oil, insoluble in ethanol, exposed to air, easy to absorb water and become aqueous sodium sulfate. It is a homogeneous polycrystalline substance, which is rhombic at 32.4 ~ 223 ℃, monoclinic crystal at higher temperature, and hexagonal crystal at 241 ℃. When crystallized from solution, it has affinity for iron, iron compounds and various organic substances; Anhydrous sodium sulfate with high purity and fine particles is called sodium sulfate.