SODIUM METABORATE

Sodium Metaborate is the sodium salt of Metaborate. 
Sodium metaborate is used in the manufacturing of borosilicate glasses. 
Sodium Metaborate is also a component of herbicides and antifreeze. 

CAS:    7775-19-1
MF:    BNaO2
MW:    65.8
EINECS:    231-891-6

Synonyms
Boric acid (HBO2), sodium salt;Boric acid, monosodium salt;Monosodium metaborate;NaBO2;Rasorite;Sodium dioxoborate;SODIUM MONOBORATE;SODIUM METABORATE

Sodium Metaborate can also be used as an oil additive with anti-wear properties. 
Sodium metaborate electroreduction in the alkaline system can act as a novel desulphurization process of coal water slurry. 
Sodium Metaborate also has role in hydrolysis of sodium borohydride to minimize the water utilization4. 
Sodium Metaborate can also act as a novel alkali in alkali/surfactant/polymer flooding. 
Sodium Metaborate is also useful in the thermo-chemical production of sodium borohydride, which is a safe and practical hydrogen storage material for on-board hydrogen production.
Also available commercially as octahydrate and tetrahydrate.
An inorganic sodium salt having metaborate as the counterion.
Sodium Metaborate is a colorless crystalline solid that serves as a Boron source in the synthesis of NaBH4. 
Sodium Metaborate finds applications in the textile industry, as well as in flame retardants and additives.

Sodium metaborate is a chemical compound of sodium, boron, and oxygen with formula NaBO2.
However, the metaborate ion is trimeric in the anhydrous solid, therefore a more correct formula is Na3B3O6 or (Na+)3[B3O6]3−. 
The formula can be written also as Na2O·B2O3 to highlight the relation to the main oxides of sodium and boron.
The name is also applied to several hydrates whose formulas can be written NaBO2·nH2O for various values of n.
The anhydrous and hydrates are colorless crystalline solids. 
The anhydrous form is hygroscopic.

Sodium metaborate, with the CAS number 7775-19-1, is an inorganic compound that typically appears as a white, crystalline solid. 
Sodium Metaborate is the sodium salt of metaboric acid and is often used in various applications, including as a buffering agent, in glass manufacturing, and in the production of certain types of ceramics. 
Sodium metaborate is soluble in water, which allows it to be utilized in aqueous solutions for various chemical processes. 
Sodium Metaborate exhibits mild alkaline properties, making it useful in pH regulation. 
Sodium Metaborate is generally considered to be non-toxic and environmentally friendly, although, like many chemical substances, it should be handled with care to avoid irritation. 
In terms of stability, sodium metaborate is relatively stable under normal conditions but should be stored in a cool, dry place away from incompatible materials. 
Overall, Sodium Metaborate's unique properties make it valuable in both industrial and laboratory settings.

Sodium metaborate Chemical Properties
Melting point: 966 °C
Boiling point: 1434 °C
density: 2.464
solubility: soluble in H2O
pka: 8.94[at 20 ℃]
form: white hexagonal crystals
color: white hexagonal, hexane crystals, crystalline
Water Solubility: g/100g solution H2O: 14.10 (0°C), 22.00 (25°C), 55.60 (100°C); solid phase, NaBO2 ·4H2O (0°C, 25°C), NaBO2 · 2H2O (100°C) [KRU93]
NIST Chemistry Reference: Sodium metaborate(7775-19-1)
EPA Substance Registry System: Sodium metaborate (7775-19-1)

Hydrates and solubility
The following hydrates crystallize from solutions of the proper composition in various temperature ranges:

tetrahydrate NaBO2·4H2O from −6 to 53.6 °C
dihydrate NaBO2·2H2O from 53.6 °C to 105 °C
hemihydrate NaBO2·0.5H2O from 105 °C to the boiling point.
Early reports of a monohydrate NaBO2·H2O have not been confirmed.

Uses
Current and proposed applications of sodium metaborate include:
Manufacture of borosilicate glasses, which are resistant to uneven or fast heating because of their small coefficient of thermal expansion.
Composition of herbicides.
Raising the pH of injected fluids for oil extraction.

Preparation
Sodium metaborate is prepared by the fusion of sodium carbonate and boron oxide B2O3 or borax Na2B4O7. 
Another way to create the compound is by the fusion of borax with sodium hydroxide at 700 °C:
B2O3 + 2 NaOH → 2 NaBO2 + H2O

The boiling point of sodium metaborate (1434 °C) is lower than that of boron oxide (1860 °C) and borax (1575 °C) In fact, while the metaborate boils without change of composition, borax gives off a vapor of sodium metaborate with a small excess of sodium oxide Na2O.
The anhydrous salt can also be prepared from the tetraborate by heating to 270 °C in vacuum.
Although not performed industrially, hydrolysis of sodium borohydride Na[BH4] with a suitable catalyst gives sodium metaborate and hydrogen gas:

Na[BH4] + 2 H2O → NaBO2 + 4 H2 (ΔH = −217 kJ/mol)