Trisodium orthoborate

Trisodium borate is a chemical compound of sodium, boron, and oxygen, with formula Na3BO3, or (Na+)3[BO3](3-). It is a sodium salt of the orthoboric acid B(OH)3.

The compound is also called trisodium orthoborate, sodium orthoborate, or just sodium borate. However, "sodium orthoborate" has been used also for a compound with formula Na4B2O5, which would correspond to an equimolar mixture of sodium metaborate NaBO2 and trisodium borate proper. and "sodium borate" is sometimes used in the generic sense, for a sodium salt with any of several other borate anions.

Preparation
Sodium carbonate Na2CO3 will react with sodium metaborate NaBO2 or boric oxide B2O3 to form the orthoborate and carbon dioxide when heated between 600 and 850 °C:
 * NaBO2 + Na2CO3 → Na3BO3 + CO2

Difficult to obtain in pure form from melts.

Reactions
When dissolved in water, the orthoborate anion partially hydrolyzes into metaborate [BO2]- and hydroxide OH-:
 * [BO3](3-) + H2O ⇌ [BO2]- + 3 OH-

Electrolysis of a solution of sodium orthoborate generates sodium perborate at the anode.