Sodium pentaborate, more properly disodium decaborate, is a chemical compound of sodium, boron, and oxygen; a salt with elemental formula NaB5O8, Na2B10O16, or Na2O·5B2O3.

This formula is often misleading as some of the water molecules are actually hydroxyl groups covalently attached to boron atoms.

The compound is used in agriculture as a boron supplement in fertilizer with various trade names such as Solubor[5] and Aquabor.

[3] It has also been tested as an additive to improve plasma electrolytic oxidation of magnesium alloys.

The latter seems more likely, since under thermogravimetric analysis the material starts to decompose at about 130 °C with partial loss of water.