Sodium perborate
Sodium perborate (PBS) is a white, odorless, water-soluble chemical compound with the chemical formula NaBO3. It crystallizes as the monohydrate, NaBO3·H2O, trihydrate, NaBO3·3H2O and tetrahydrate, NaBO3·4H2O. The monohydrate and tetrahydrate are the commercially important forms. The elementary structural unit of sodium perborates is a dimer anion B2O4(OH)4, in which two boron atoms are joined by two peroxo bridges in a chair-shaped 6-membered ring, and the simplistic NaBO3·nH2O-type formulas are just a convenient way to express the average chemical composition.