What is "peroxydisulfate"

The peroxydisulfate ion, , is a oxyanion. It is commonly referred to as the persulfate ion, but this term also refers to the peroxomonosulfate ion, . Approximately 500,000 tons of salts containing this anion are produced annually. Important salts include sodium persulfate (NaSO), potassium persulfate (KSO), and ammonium persulfate ((NH)SO). These salts are colourless, water-soluble solids that are strong oxidants.