Sodium Sulfate

Sodium sulfate is the sodium salt of sulfuric acid. When anhydrous, it is a white crystalline solid of formula Na₂SO₄ known as the mineral thenardite; the decahydrate Na₂SO₄·10H₂O has been known as Glauber's salt or, historically, sal mirabilis since the 17th century. Another solid is the heptahydrate, which transforms to mirabilite when cooled. With an annual production of 6 million tonnes, it is a major commodity chemical product.

Sodium sulfate is mainly used for the manufacture of detergents and in the Kraft process of paper pulping. About two-thirds of the world's production is from mirabilite, the natural mineral form of the decahydrate, and the remainder from by-products of chemical processes such as hydrochloric acid production.