Sodium sulfate — also known as sodium sulphate, sulfate of soda, or CAS No. 7757-82-6 — is an inorganic compound of sodium. This sodium salt form of sulfuric acid is extensively used in a wide range of industries. More than 6.5 million tons of sodium sulfate are produced each year around the world. Most are mined from the compound's natural mineral form called mirabilite, which is taken from lake beds as part of the water treatment process. Another one-third is produced as a byproduct of other processes in the chemical industry.