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Sodium perborate
Sodium perborate are chemical compounds with chemical formula [Na+]2[B2O4(OH)4]2−(H2O)x. Commonly encountered salts are the anhydrous form (x = 0) and as a hexahydrate (x = 6). These two species are sometimes called, respectively, "monohydrate" or PBS-1 and "tetrahydrate" or PBS-4, after the historic assumption that NaBO3 would be the anhydrous form). Both the anhydrous and hexahydrate salts are white, odorless, water-soluble solids.
Peroxyborates are widely used in laundry detergents, as one of the peroxide-based bleaches.
Sodium perborate was first obtained in 1898, independently, by Sebastian Tanatar and by P. Melikoff and L. Pissadewsky; the researchers prepared sodium perborate by treating sodium borate with a solution of hydrogen peroxide and sodium hydroxide, but Tanatar also obtained sodium perborate by electrolysis of a solution of sodium borate.
Unlike sodium percarbonate, the peroxyborates are not adducts of hydrogen peroxide. Rather, they contain a peroxyborate anion [(B(OH)2OO)2]2−, which consists of a cyclic −B−O−O−B−O−O− core with a pair of hydroxy groups bonded to each boron atom. The ring adopts a chair conformation. The hexahydrate has the formula Na2H4B2O8·6H2O, that is, Na2H16B2O14 or NaH8BO7.
The anhydrous compound is commonly but incorrectly called a "monohydrate" with the historical but misleading formula NaBO3·H2O. Instead, a more descriptive formula is Na2[(HO)2B]2(O2)2. Likewise, the hexahydrate is usually called "tetrahydrate" and formulated as NaBO3·4H2O. Both forms are white, odorless, water-soluble solids. The "monohydrate" and the "tetrahydrate" are the commercially important forms.
A true tetrahydrate Na2H4B2O8·4H2O, traditionally known as the "trihydrate", is also known but has no industrial significance. There is a CAS number for each of the three traditional "hydrates", the three "peroxyborate" versions of each (interpreted as a hydrogen peroxide adduct) and the poorly defined "anhydrate" NaBO3, a total of seven.
Sodium perborate hydrolyzes (i.e. breaks down in contact with water), producing hydrogen peroxide and borate:
The resulting hydroperoxide then enter in equilibrium with boric acid B(OH)3, hydrogen peroxide H2O2, the hydroperoxyl anion −OOH, and the tetrahydroxyborate anion [B(OH)4]−:
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Sodium perborate
Sodium perborate are chemical compounds with chemical formula [Na+]2[B2O4(OH)4]2−(H2O)x. Commonly encountered salts are the anhydrous form (x = 0) and as a hexahydrate (x = 6). These two species are sometimes called, respectively, "monohydrate" or PBS-1 and "tetrahydrate" or PBS-4, after the historic assumption that NaBO3 would be the anhydrous form). Both the anhydrous and hexahydrate salts are white, odorless, water-soluble solids.
Peroxyborates are widely used in laundry detergents, as one of the peroxide-based bleaches.
Sodium perborate was first obtained in 1898, independently, by Sebastian Tanatar and by P. Melikoff and L. Pissadewsky; the researchers prepared sodium perborate by treating sodium borate with a solution of hydrogen peroxide and sodium hydroxide, but Tanatar also obtained sodium perborate by electrolysis of a solution of sodium borate.
Unlike sodium percarbonate, the peroxyborates are not adducts of hydrogen peroxide. Rather, they contain a peroxyborate anion [(B(OH)2OO)2]2−, which consists of a cyclic −B−O−O−B−O−O− core with a pair of hydroxy groups bonded to each boron atom. The ring adopts a chair conformation. The hexahydrate has the formula Na2H4B2O8·6H2O, that is, Na2H16B2O14 or NaH8BO7.
The anhydrous compound is commonly but incorrectly called a "monohydrate" with the historical but misleading formula NaBO3·H2O. Instead, a more descriptive formula is Na2[(HO)2B]2(O2)2. Likewise, the hexahydrate is usually called "tetrahydrate" and formulated as NaBO3·4H2O. Both forms are white, odorless, water-soluble solids. The "monohydrate" and the "tetrahydrate" are the commercially important forms.
A true tetrahydrate Na2H4B2O8·4H2O, traditionally known as the "trihydrate", is also known but has no industrial significance. There is a CAS number for each of the three traditional "hydrates", the three "peroxyborate" versions of each (interpreted as a hydrogen peroxide adduct) and the poorly defined "anhydrate" NaBO3, a total of seven.
Sodium perborate hydrolyzes (i.e. breaks down in contact with water), producing hydrogen peroxide and borate:
The resulting hydroperoxide then enter in equilibrium with boric acid B(OH)3, hydrogen peroxide H2O2, the hydroperoxyl anion −OOH, and the tetrahydroxyborate anion [B(OH)4]−: