Trisodium orthoborate

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Trisodium orthoborate is a chemical made from sodium, boron, and oxygen, with the formula Na3BO3. It is the sodium salt of orthoboric acid (B(OH)3) and is also called trisodium borate, sodium orthoborate, or sodium borate. Note that the name “sodium orthoborate” has sometimes been used for a different compound, Na4B2O5, and “sodium borate” can refer to sodium salts with other borate units.

This compound is difficult to obtain in pure form from melts. When heated with sodium carbonate (Na2CO3) between about 600 and 850 °C, Na2CO3 can react with sodium metaborate (NaBO2) or boric oxide (B2O3) to form orthoborate and carbon dioxide. In water, the orthoborate ion partially hydrolyzes to metaborate (BO2−) and hydroxide (OH−). If a solution of sodium orthoborate is electrolyzed, sodium perborate can form at the anode.

Properties:
- Formula: Na3BO3
- Molar mass: ~127.78 g/mol
- Density: ~1.73 g/cm3
- Melting point: 75 °C
- Boiling point: 320 °C

Hazards: it can irritate eyes and skin, so appropriate precautions should be used when handling.

Related compounds include borax (sodium tetraborate), sodium pentaborate, disodium octaborate, disodium enneaborate, and sodium metaborate.