sodium sulfate decahydrate, also known as Glauber’s salt, is the common form of sodium sulfate in use. It is an alkali, and it is used to dry organic liquids and as a filler in powdered home laundry detergents. It is also used as a fining agent to remove small air bubbles from molten glass. It is also used as a coagulant in the Kraft process of paper pulping, and in some metallurgical processes. Sodium sulfate is a component of several household cleaners, such as the brand name SOS (Sodium Sulfate Solution).
The crystalline structure of sodium sulfate depends on whether it has water molecules in it or not: Anhydrous sodium sulfate has no water and is thus dry; the decahydrate has 12 water molecules and is therefore wet. The other natural forms of sodium sulfate are the anhydrous heptahydrate and the octahydrate, both of which are very rare; they occur in saline lakes such as the Great Salt Lake in Utah. The sulfate mineral thenardite is also found in the desert, and it is used as a drying agent in the chemical industry.
The most investigated salt hydrate of sodium sulfate is its decahydrate form, which has a relatively large latent thermal energy storage density and is inexpensive. It has been impregnated into porous adsorption materials such as attapulgite and expanded perlite to prepare binary eutectic hydrated salts, which are then used in shape-stabilized phase change materials for building energy conservation.