Many sodium borates have important industrial and household applications; the best known being borax, (Na+)2[B4O5(OH)4]2−·8H2O = Na2B4H20O17.
[1] Sodium borates, as well as boroxy acids, are often described as mixtures xNa2O·yB2O3·zH2O = Na2xB2yH2zOx+3y+z, with x, y, and z chosen to fit the elemental formula, or a multiple thereof.
However, later research uncovered that many borates have hydroxyl groups HO− bound covalently to the boron atoms in the anion.
[6] Some sodium borates hower cannot be analyzed as combinations xNa2O·yB2O3·zH2O of the three ordinary oxides.
The anion of this compound has two peroxide bridges −O−O− which make it oxygen-rich compared to the general family above.