Trisodium orthoborate

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

Trisodium orthoborate

Names
IUPAC name Trisodium orthoborate
Other names Sodium, boric acid salt Sodium orthoborate Sodium borate
Identifiers
CAS Number	14312-40-4 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL38909 N
ChemSpider	140167 N
Gmelin Reference	117865
PubChem CID	159383
CompTox Dashboard (EPA)	DTXSID1049776
InChI InChI=1S/BO3.3Na/c2-1(3)4;;;/q-3;3*+1 N Key: BSVBQGMMJUBVOD-UHFFFAOYSA-N N
SMILES B([O-])([O-])[O-].[Na+].[Na+].[Na+]
Properties
Chemical formula	Na3BO3
Molar mass	127.78 g·mol−1
Density	1.73 g/cm3[1]
Melting point	75 °C (167 °F; 348 K) [1]
Boiling point	320 °C (608 °F; 593 K) [1]
Hazards
GHS labelling:[2]
Pictograms
Signal word	Warning
Hazard statements	H319, H360, H361d, H412
Precautionary statements	P203, P264+P265, P273, P280, P305+P351+P338, P318, P337+P317, P405, P501
Related compounds
Related compounds	Borax Sodium pentaborate Disodium octaborate Disodium enneaborate Sodium metaborate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[4] 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:^[3]

NaBO₂ + Na₂CO₃ → Na₃BO₃ + CO₂

Difficult to obtain in pure form from melts.^[5]

Properties

Reactions

When dissolved in water, the orthoborate anion partially hydrolyzes into metaborate [BO₂]⁻ and hydroxide OH⁻:^[3]

[BO₃]³⁻ + H₂O ⇌ [BO₂]⁻ + 2 OH⁻

Electrolysis of a solution of sodium orthoborate generates sodium perborate at the anode.^{[6] [7]}