What is the formula for potassium borate?

Answer 1

There are two common commercially available forms of potassium borate:

1) Potassium tetraborate has the structural formula K2[B4O5(OH)4].2H2O. The formula for potassium tetraborate is often written as K2B4O7.xH2O or as the oxide form, K2O.2B2O3.8H2O. This compound can be regarded as the potassium analogue of the sodium tetraborate commonly called borax.

2) Potassium pentaborate has the structural formula K[B5O6(OH)4].2H2O. The formula for potassium pentaborate is alternatively written as KB5O8.4H2O (or K2B10O16.8H2O) or in the oxide form as K2O.5B2O3.8H2O.

A number of other crystalline potassium borates exit, including potassium metaborates, K[B(OH)4].xH2O (or KBO2.xH2O).

These common forms of potassium borate have anhydrous counterparts prepared by fusing the hydrated borates.