Trisodium orthoborate
# Trisodium orthoborate

Trisodium borate is a chemical compound of sodium, boron, and oxygen, with formula $Na_3BO_3,$ or $(Na^+)_3[BO_3]^{3−}.$ 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 $Na_4B_2O_5,$ which would correspond to an equimolar mixture of sodium metaborate $NaBO_2$ 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 $Na_2CO_3$ will react with sodium metaborate $NaBO_2$ or boric oxide $B_2O_3$ to form the orthoborate and carbon dioxide when heated between 600 and 850 °C:

    $NaBO_2$ + $Na_2CO_3$ → $Na_3BO_3$ + $CO_2$

Difficult to obtain in pure form from melts.

## Reactions

When dissolved in water, the orthoborate anion partially hydrolyzes into metaborate $[BO_2]^−$ and hydroxide $OH^−:$

    $[BO_3]^{3−}$ + $H_2O$ ⇌ $[BO_2]^−$ + 3 $OH^−$

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

