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; thedecahydrate Na₂SO₄·10H₂O is found naturally as the mineral mirabilite, and in processed form has been known as Glauber's salt or, historically, salt mirabilis since the 17th century. With an annual production of 6 million tones, it is a majorcommodity chemical product.

Use in Soaps and Detergents 
A large amount of sodium sulfate has been used in powdered detergents as filler. However, sodium sulfate use has begun declining as well; the need for filler has gone down, due to the trend toward using concentrated liquid detergents instead of bulkier powder formulas. It is still used in carpet powders and window defrosting applications. 
Textiles 
Approximately 100,000 tons of sodium sulfate is utilized annually for dyeing textiles. It does not corrode the stainless steel vessels as sodium chloride (which can also be used in this manner) does. Sodium sulfate is a leveling agent, reducing negative chargers on the fibers, which allows the dyes to penetrate evenly. Sodium sulfate is a by-product of rayon production. 
Wood Pulp 
One notable use for sodium sulfate compound is in the Kraft process, also known as the sulfate process, of wood pulp manufacturing which is widely used to make paper products and building supplies .The technology involves impregnating wood chips with sodium sulfate; the wood is heated, causing a reduction of the sodium sulfate into sodium sulfide. This breaks the bond in the cellulose of the wood, making it malleable and able to be extruded. 
Glass 
Sodium sulfate is used in the glass industry as well. Sodium sulfate prevents scum formation by the molten glass during refining, and also fluxes the glass. The compound also acts as a fining agent in molten glass, removing small air bubbles and imperfections during the blowing and casting processes. 
Drying and Thermal Storage 
In the laboratory, sodium sulfate is often used as an inert drying compound for organic materials. It removes water from compounds reliably at temperatures below 30° C (86° F). Another main use of sodium sulfate is in thermal storage. It has been utilized as a solar heat storage component, because it has a high heat storage capacity and does not change from a solid to a liquid until 90 ° F (32 ° C). Sodium sulfate is used to store heat in thermal tiles, and put into cells surrounded by solar-heated water, as well as in some computer-cooling and insulating applications.