Anhydrous sodium carbonate is the waterless crystalline form of sodium carbonate, the sodium salt of carbonic acid. Its chemical formula is Na2CO3, and its molar mass is 105.988 grams per mole. Its density is 2.54 grams per cubic centimeter. It is soluble in water and slightly soluble in aqueous alcohol.
Anhydrous sodium carbonate is a hygroscopic white substance. Various hydrated crystals are also known, including a monohydrate, heptahydrate and decahydrate, all of which have different densities and water solubilities. The anhydrous form is found rarely in nature in a mineral called natrite. Sodium carbonate is used domestically as a water softener used in laundering.