Trisodium pentaborate
# Trisodium pentaborate

Trisodium pentaborate is a salt that can form as a monohydrate with formula $Na_3B_5O_8(OH)_2·H_2O,$ which contains the anion dihydroxydopentaborate $[B_5O_8(OH)_2]^{3−}.$

Its formula may be incorrectly given as $Na_3B_5O_8·2H_2O,$ or as $3Na_2O_5B_2O_3·4H_2O.$ It may also be called simply sodium pentaborate, but this name is more properly reserved for the compound with elemental formula $Na_2O·5B_2O_3·nH_2O.$

## Structure

Trisodium pentaborate monohydrate crystallizes as thin plates in the orthorhombic crystal system, with symmetry group Pbca and cell parameters a = 880.4 pm, b = 1837.1 pm, c = 1092.4 pm, formulas per cell Z = 8.

