Boric acid is a naturally occurring inorganic acid that plays a direct role in calcium metabolism in mammals and is considered a vital micronutrient, however toxic at high concentrations in animals. It is hydrogen borate, a weak boron acid.

The name describes the structure of the molecule:.

• Boric refers to boron, the central chemical element in this compound. Boric acid is a weak compound of boron and oxygen, often used for its antiseptic, antifungal, and insecticidal properties.
• acid indicates that the substance is an acid, a class of chemical compounds characterized by specific chemical properties, such as the ability to donate hydrogen ions.

Raw Materials and Their Functions

Borate Minerals. Natural sources of boron, such as boracite, sassolite, and kernite, from which boric acid can be extracted.

Water. Used as a solvent in the process of extracting and purifying boric acid from borate minerals.

Industrial Chemical Synthesis of Boric Acid

• Extraction. Boric acid is extracted from borate minerals. This process can include dissolving the minerals in water followed by further chemical reactions to isolate boric acid.
• Purification. After extraction, boric acid is purified to remove impurities and concentrate the compound.
• Crystallization. The purified boric acid is crystallized to form solid crystals.
• Quality Control and Packaging. The crystallized boric acid undergoes quality checks to ensure it meets the required standards. After quality control, it is packaged for use in a variety of applications, such as pharmaceuticals, cosmetics, personal care products, and as a pH regulator in swimming pools, etc.

It appears in the form of a white powder consisting of colourless water-soluble crystals or an odourless white amorphous powder.

What it is used for and where

Boric Acid is commonly used as an antiseptic in pharmaceutical products, as a preservative in some ophthalmic solutions, and as an ingredient in insecticides and plant care products. It is also used in some industrial applications, such as in the manufacture of glass and ceramics.

It was originally registered in the USA as a household insecticide and is still an effective and commonly used product to control a wide range of pests in public health, agricultural, and structural settings.

Medical

It has anti-inflammatory and antioxidant properties that have made it useful in various therapies.

It has been used for decades to treat yeast vaginitis, bacterial vaginosis, recurrent vulvovaginal candidiasis, and the additional use of boric acid in non-surgical periodontal therapy has been shown to be effective in treatment at 3 and 6 months (1).

Other studies have demonstrated the efficacy of boric acid against drug-resistant Candida albicans and Candida glabrata (2). 

In ophthalmology it is used as an excipient in eye drops and as a multipurpose solution for tamponaded contact lenses as a disinfectant and without cytotoxic effects (3).

Food

Ingredient listed in the European food additives list as E284, preservative.

Food safety

The Panel on Food Additives evaluated the safety of boric acid (E 284) and sodium tetraborate (borax) (E 285) as food additives in the EU. These additives are authorised in the EU for use as preservatives in sturgeon eggs (caviar) up to a maximum concentration of 4 g boric acid/kg.  An ADI of 0.16 mg boron/kg body weight/day was established.  The Panel concluded that boric acid and sodium tetraborate are not of concern in terms of genotoxicity (4)

Cosmetics

It is a restricted ingredient II/1395 as Relevant Item in the Annexes of the European Cosmetics Regulation No. 2019/831 (5).

Antimicrobial agent. This ingredient is able to suppress or inhibit the growth and replication of a broad spectrum of microorganisms such as bacteria, fungi and viruses by making the stratum corneum temporarily bactericidal and fungicidal.

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.

Denaturant. The ionic or polar molecules of this ingredient included in formulations that interact with protein groups, modulate the properties of the solution to suit specific needs.

Other uses

Boric acid is widely used by the glass industry, particularly for glass fibres, in ceramics to improve strength and lustre. It is also used in metal welding, electronics, precious stones and scientific research.

For more information:

Boric acid studies

Typical commercial product characteristics Boric acid

• Molecular Formula  H₃BO₃     B(OH)₃    BH₃O₃
• Molecular Weight     61.84
• Exact Mass    62.017525
• CAS  10043-35-3
• UNII    R57ZHV85D4
• EC Number   233-139-2
• DSSTox Substance ID  DTXSID1020194
• IUPAC  boric acid
• InChI=1S/BH3O3/c2-1(3)4/h2-4H 
• InChl Key      KGBXLFKZBHKPEV-UHFFFAOYSA-N
• SMILES   B(O)(O)O
• MDL number  MFCD00011337
• PubChem Substance ID    329773111
• ChEBI  33118
• NCI    C47416
• ICSC    0991
• RXCUI    1700  
• RTECS   ED4550000
• eCl@ss      38120104
• NACRES NA.21

Price  500g    €42,80

Synonyms

• Orthoboric acid
• Boracic acid
• Trihydroxyborone
• Boron hydroxide

References________________________________________________________________________

(1) Bashir NZ, Krstic M. Boric acid as an adjunct to periodontal therapy: A systematic review and meta-analysis. Int J Dent Hyg. 2021 May;19(2):139-152. doi: 10.1111/idh.12487.

(2) Larsen B, Petrovic M, De Seta F. Boric Acid and Commercial Organoboron Products as Inhibitors of Drug-Resistant Candida albicans. Mycopathologia. 2018 Apr;183(2):349-357. doi: 10.1007/s11046-017-0209-6.

(3) Lehmann DM, Cavet ME, Richardson ME. Nonclinical safety evaluation of boric acid and a novel borate-buffered contact lens multi-purpose solution, Biotrue™ multi-purpose solution. Cont Lens Anterior Eye. 2010 Dec;33 Suppl 1:S24-32. doi: 10.1016/j.clae.2010.06.010.

Kikuchi T, Suzuki M, Kusai A, Iseki K, Sasaki H. Synergistic effect of EDTA and boric acid on corneal penetration of CS-088. Int J Pharm. 2005 Feb 16;290(1-2):83-9. doi: 10.1016/j.ijpharm.2004.11.019.

(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) Opinion of the Scientific Committee on Consumer Safety on boron compounds (CMR) (europa.eu)