Borax or Sodium Tetraborate or Sodium borate, is a mineral and chemical compound in the refined form of natural sodium borate. It is composed of boron trioxide, sodium oxide and water.

Description of the raw materials:

• Boracite - A boron mineral from which borax is extracted. Boracite is found in evaporite deposits in various parts of the world.
• Water - Water is used in the extraction and purification process of borax.

Borax can be found in nature in the form of minerals such as borax. Therefore, its natural synthesis involves the process of extracting and purifying borax-containing minerals.

• Extraction of borax mineral. The borax-containing mineral is extracted from the mine or natural sources.
• Refining. The borax mineral undergoes refining processes to remove any impurities and obtain a pure Borax product.
• Purification. The extracted Borax is purified through washing and filtration processes to remove any residual impurities.
• Drying. The purified Borax is dried to remove residual moisture and obtain a solid product.
• Crushing and grinding. The solid product is crushed and ground to obtain the desired form, such as powder or crystals.

Summary of the industrial chemical synthesis process:

• Preparation of reagents. The reagents needed for the synthesis of Borax, such as boric acid and sodium carbonate, are collected and prepared.
• Chemical reaction. Boric acid and sodium carbonate react with each other in a reactive system, such as a chemical reactor, to form sodium borate, which is Borax.
• Crystallization. The solution containing sodium borate is cooled and subjected to crystallization processes to precipitate Borax crystals.
• Filtration and washing. The Borax crystals are separated from the solution through filtration and washing processes to remove any impurities or residues.
• Drying. The Borax crystals are dried to remove moisture and obtain a solid product.
• Crushing and grinding. The solid product is crushed and ground to obtain the desired form of Borax, such as powder or crystals.
• Packaging of Borax in appropriate containers for distribution and use.

It appears as a white, crystalline, alkaline granular powder that melts in glass at 878°C. Easily soluble in water and glycerine, it is efflorescent when exposed to dry air.

What it is used for and where

Medical

The addition of borax, for tissue engineering applications on mesenchymal stem cells, induces osteogenesis by stimulating growth factor receptors and fibronectin-binding integrins (1).

The use of borax or boric acid buffers in ophthalmology is also approved by the Medicines and Healthcare products Regulatory Agency for paediatric use in children under 2 years of age (2). It acts as a mild antiseptic and cleaning agent.

In biomedicine, borax hydrogels, together with locust bean gum and gellan gum, have demonstrated good mechanical properties with excellent self-healing and thermo-processability properties (3).

Present in tooth-whitening formulas.

Food

A food additive labelled E285 on the European food additive list as a preservative, but banned in the US, Thailand, China and the current trend is to reduce or eliminate its use. In 2013, the European Food Safety Authority (EFSA) stated that boric acid and its salts are toxicologically acceptable as preservatives in caviar as the intake of this expensive fish product does not occur on a regular basis and it is considered unlikely that the boron dose of 0.16 mg per kg body weight/day (ADI) would be exceeded (4).

Safety

Borax is toxic to humans and can induce reproductive and developmental toxicity, neurotoxicity and nephrotoxicity.

Borax concentrations above 52 mM (20 mg mL^-1) are toxic to cells, while borax concentrations above 15.7 mM (6 mg mL^-1) inhibit the formation of myotubes (5), a type of cell that develops into muscle fibres.

Jewellery

Melting metals such as gold and silver and for their cleaning as borax removes oxides on the metal surface and, when mixed with water, improves melting point uniformity. It softens tungsten in pre-soldering with zinc and improves solderability.

Replaces mercury in gold mining in small-scale mines with less toxic characteristics.

Cosmetics

It is a restricted ingredient as II/1396 a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported: Boric acid, Borates and Tetraborates, Sodium Perborate and Perboric Acid

• Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Agriculture

It is considered a dynamic covalent cross-linking agent as a water retention agent.

Insecticides

Useful as an ant and insect repellent.

Biochemistry

Used as a buffer in biochemical and chemical laboratories and nucleic acid buffer most commonly used in DNA gel electrophoresis, as TBE or BBS, saline buffered borate gel, SB, gel without chemical reactions or solvents, SB or BBS (saline buffered borate) in coating procedures. Borate buffers (usually pH 8) are also used as the preferred equilibrium solution in DMP-based cross-linking reactions. 

Other uses

Chemical cross-linking agent. Flame retardant in insulation products in fireproofing paints, textile stain removal, porcelain manufacture.

Glass. Production of high quality glass. Raw material for boron oxide in the manufacture of thermally insulated glass wool, heat-resistant glass, borosilicate glass, glass fibre weaving, optical glasses, sealing glass.

Metals.  When welding iron and steel, mixed borax and ammonium chloride are used to lower the melting point of unwanted iron oxide. In metal drawing it functions as a lubricant carrier.

Construction. Slackener in cement and concrete. 

Chemical industry. In paraffin production it is the pH value buffering agent in the water system and emulsifier.

Water treatment.

In compounds containing boron, borax is the basic raw material.

Fertiliser in agriculture.

Also: detergent, rust binder, fire retardant, emulsifier, stabiliser etc.

For more information:    

Borax studies

Typical commercial product characteristics Sodium tetraborate decahydrate

Appearance	White granular powder
Boiling Point	320°C
Melting Point	75°C
Density	1.73 g/mL at 25°C(lit.)
PSA	184.57000
Water Solubility	60 g/L (20 ºC)
Boron monoxide B2O	≥ 36.47%
Sulfur dioxide SO2	≤ 0.1%
Chloride Cl	≤ 0.05%
Iron Fe	≤ 0.001%
Sodium oxide Na2O	≥16%
Boron trioxide B2O3	≥ 35%
Insoluble in water	0.04% Max
Safety

• Molecular Formula    B₄H₂₀Na₂O₁₇      B₄O₇Na₂. 10H₂O    
• Linear Formula   Na₂B₄O7 · 10H₂O
• Molecular Weight     381.4
• Exact Mass    382.086823
• CAS  1303-96-4
• UNII    91MBZ8H3QO
• EC Number   603-411-9    215-540-4    
• DSSTox Substance ID  DTXSID701014356    DTXSID2034384
• IUPAC  disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane;decahydrate
• InChI=1S/B4O7.2Na.10H2O/c5-1-7-3-9-2(6)10-4(8-1)11-3;;;;;;;;;;;;/h;;;10*1H2/q-2;2*+1;;;;;;;;;;
• InChl Key      CDMADVZSLOHIFP-UHFFFAOYSA-N
• SMILES   B1(OB2OB(OB(O1)O2)[O-])[O-].O.O.O.O.O.O.O.O.O.O.[Na+].[Na+]
• MDL number  MFCD00149193
• PubChem Substance ID    329824630
• RXCUI    36680   
• ICSC    0567
• NACRES NA.21  
• RTECS   VZ2275000

Synonyms

• Sodium tetraborate decahydrate
• Borax decahydrate
• Sodium borate decahydrate
• Sodium pyroborate decahydrate

References_______________________________________________________

(1) Rico P, Rodrigo-Navarro A, Sánchez Pérez L, Salmeron-Sanchez M. Borax induces osteogenesis by stimulating NaBC1 transporter via activation of BMP pathway. Commun Biol. 2020 Nov 27;3(1):717. doi: 10.1038/s42003-020-01449-4. 

(2) Chloramphenicol eye drops: ok to use in children younger than 2 years. Drug Ther Bull. 2021 Sep;59(9):133. doi: 10.1136/dtb.2021.000045. 

(3) Lv Y, Pan Z, Song C, Chen Y, Qian X. Locust bean gum/gellan gum double-network hydrogels with superior self-healing and pH-driven shape-memory properties. Soft Matter. 2019 Aug 14;15(30):6171-6179. doi: 10.1039/c9sm00861f. 

(4) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). (2013). Scientific Opinion on the re‐evaluation of boric acid (E 284) and sodium tetraborate (borax)(E 285) as food additives. EFSA Journal, 11(10), 3407.

(5) Ciriza J, Rodríguez-Romano A, Nogueroles I, Gallego-Ferrer G, Cabezuelo RM, Pedraz JL, Rico P. Borax-loaded injectable alginate hydrogels promote muscle regeneration in vivo after an injury. Mater Sci Eng C Mater Biol Appl. 2021 Apr;123:112003. doi: 10.1016/j.msec.2021.112003.