Boric acid

Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula Template:Chem2. It may also be called hydrogen orthoborate, trihydroxidoboron or boracic acid.<ref name=webster/> It is usually encountered as colorless crystals or a white powder, that dissolves in water, and occurs in nature as the mineral sassolite. It is a weak acid that yields various borate anions and salts, and can react with alcohols to form borate esters.

Boric acid is often used as an antiseptic, insecticide, flame retardant, neutron absorber, or precursor to other boron compounds.

The term "boric acid" is also used generically for any oxyacid of boron, such as metaboric acid Template:Chem2 and tetraboric acid Template:Chem2.

History

Orthoboric acid was first prepared by Wilhelm Homberg (1652–1715) from borax, by the action of mineral acids, and was given the name {{#invoke:Lang|lang}} ("sedative salt of Homberg"). However, boric acid and borates have been used since the time of the ancient Greeks for cleaning, preserving food, and other uses.<ref name=eisler2007/>

Molecular and crystal structure

The three oxygen atoms form a trigonal planar geometry around the boron. The B-O bond length is 136 pm, and the O-H is 97 pm. The molecular point group is C_3h.<ref>Template:Greenwood&Earnshaw2nd</ref>

Two crystalline forms of orthoboric acid are known: triclinic with space group PTemplate:Overline, and trigonal with space group P3₂. The former is the most common; the second, which is a bit more stable thermodynamically, can be obtained with a special preparation method.<ref name=rota2017/>

The triclinic form of boric acid consists of layers of Template:Chem2 molecules held together by hydrogen bonds with an O...O separation of 272 pm. The distance between two adjacent layers is 318 pm.<ref name=GandE/> While the layers of the triclinic phase are nearly trigonal with Template:Nowrap, Template:Nowrap, and Template:Nowrap (compared to Template:Nowrap for the trigonal form), the stacking of the layers is somewhat offset in the triclinic phase, with Template:Nowrap and Template:Nowrap. The triclinic phase has Template:Nowrap and the trigonal one has Template:Nowrap.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

File:Boric-acid-unit-cell-3D-balls.png	File:Boric-acid-layer-3D-balls.png
The unit cell of boric acid {{safesubst:#invoke:Check for unknown parameters|check|unknown=|preview=Page using Template:Center with unknown parameter "_VALUE_"|ignoreblank=y| 1 | style }}	hydrogen bonding (dashed lines) allows boric acid molecules to form parallel layers in the solid state {{safesubst:#invoke:Check for unknown parameters|check|unknown=|preview=Page using Template:Center with unknown parameter "_VALUE_"|ignoreblank=y| 1 | style }}

Preparation

Boric acid may be prepared by reacting borax (sodium tetraborate decahydrate) with a mineral acid, such as hydrochloric acid:

Template:Chem2·10Template:Chem2 + 2 HCl → 4 Template:Chem2 + 2 NaCl + 5 Template:Chem2

It is also formed as a byproduct of hydrolysis of boron trihalides and diborane:<ref name=hous2008/>

Template:Chem2 + 6 Template:Chem2 → 2 Template:Chem2 + 6 Template:Chem2

Template:Chem2 + 3 Template:Chem2 → Template:Chem2 + 3 HX (X = Cl, Br, I)

Reactions

Pyrolysis

When heated, orthoboric acid undergoes a three-step dehydration. The reported transition temperatures vary substantially from source to source.Template:Citation needed

When heated above 140 °C, orthoboric acid yields metaboric acid (Template:Chem2) with loss of one water molecule:<ref name=kaur2021/><ref name=aghi2018/>

Template:Chem2 → Template:Chem2 + Template:Chem2

Heating metaboric acid above about 180 °C eliminates another water molecule forming tetraboric acid, also called pyroboric acid (Template:Chem2):<ref name=kaur2021/><ref name=aghi2018/>

4 Template:Chem2 → Template:Chem2 + Template:Chem2

Further heating (to about 530 °C) leads to boron trioxide:<ref name=balci2012/><ref name=kaur2021/><ref name=aghi2018/>

Template:Chem2 → 2 Template:Chem2 + Template:Chem2

Aqueous solution

When orthoboric acid is dissolved in water, it partially dissociates to give metaboric acid:

Template:Chem2 Template:Eqm Template:Chem2 + Template:Chem2

The solution is mildly acidic due to the ionization of the acids:

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2 + Template:H3O+

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2 + Template:H3O+

However, Raman spectroscopy of strongly alkaline solutions has shown the presence of [[tetrahydroxyborate|Template:Chem2 ions]],<ref name=jolly1984/> leading some to conclude that the acidity is exclusively due to the abstraction of Template:Chem2 from water:<ref name=jolly1984/>

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2

Equivalently,

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2 + Template:H+ (K_a = 7.3×10⁻¹⁰; pK_a = 9.14)

Or, more properly,

Template:Chem2 + 2 Template:Chem2 Template:Eqm Template:Chem2 + Template:H3O+

This reaction occurs in two steps, with the neutral complex aquatrihydroxyboron Template:Chem2 as an intermediate:<ref name=tachi2004/>

Template:Chem2 + Template:Chem2 → Template:Chem2

Template:Chem2 + Template:Chem2 → Template:Chem2 + Template:H3O+

This reaction may be characterized as Lewis acidity of boron toward Template:Chem2, rather than as Brønsted acidity.<ref name=hous2005/><ref name=JEE2014/><ref name=darp2000/> However, some of its behaviour towards some chemical reactions suggest it to be a tribasic acid in the Brønsted-Lowry sense as well.

Boric acid, mixed with borax Template:Chem2 (more properly Template:Chem2) in the weight ratio of 4:5, is highly soluble in water, though they are not so soluble separately.<ref name=tsuy2007/>

Sulfuric acid solution

Boric acid also dissolves in anhydrous sulfuric acid according to the equation:<ref name=GandE/>

Template:Chem2 + 6 Template:Chem2 → Template:Chem2 + 2 Template:Chem2 + 3 Template:H3O+

The product is an extremely strong acid, even stronger than the original sulfuric acid.<ref name=GandE/>

Esterification

Boric acid reacts with alcohols to form borate esters, Template:Chem2 where R is alkyl or aryl. The reaction is typically driven by a dehydrating agent, such as concentrated sulfuric acid:<ref name=brown1956/>

Template:Chem2 + 3 ROH → Template:Chem2 + 3 Template:Chem2

With vicinal diols

The acidity of boric acid solutions is considerably increased in the presence of cis-vicinal diols (organic compounds containing similarly oriented hydroxyl groups in adjacent carbon atoms, Template:Chem2) such as glycerol and mannitol.<ref name=vogelP357/><ref name=GandE/><ref name=NIST1969/><ref name="Belcher1960"/>

The tetrahydroxyborate anion formed in the dissolution spontaneously reacts with these diols to form relatively stable anion esters containing one or two five-member Template:Chem2 rings. For example, the reaction with mannitol Template:Chem2, whose two middle hydroxyls are in cis orientation, can be written as:

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2 + Template:Chem2

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2 + 2 Template:Chem2

Template:Chem2 + Template:Chem2 Template:Eqm Template:Chem2 + 2 Template:Chem2

Giving the overall reaction:

Template:Chem2 + 2 Template:Chem2 Template:Eqm Template:Chem2 + 3 Template:Chem2 + Template:Chem2

The stability of these mannitoborate ester anions shifts the equilibrium to the right, thereby increasing the solution's acidity by five orders of magnitude compared to that of pure boric oxide. This lowers the pK_a from 9 to below 4 for a sufficient concentration of mannitol.<ref name=vogelP357/><ref name=GandE/><ref name=NIST1969/><ref name="Belcher1960"/> The resulting solution is referred to as mannitoboric acid.

The addition of mannitol to an initially neutral solution containing boric acid or simple borates lowers its pH enough for it to be titrated by a strong base such as NaOH, including with an automated potentiometric titrator. This property is used in analytical chemistry to determine the borate content of aqueous solutions, for example to monitor the depletion of boric acid by neutrons in the water of the primary circuit of light-water reactor when the compound is added as a neutron poison during refueling operations.<ref name=GandE/>

Toxicology

Based on mammalian median lethal dose (LD₅₀) rating of 2,660 mg/kg body mass, boric acid is only poisonous if taken internally or inhaled in large quantities. The Fourteenth Edition of the Merck Index indicates that the LD₅₀ of boric acid is 5.14 g/kg for oral dosages given to rats, and that 5 to 20 g/kg has produced death in adult humans. For a 70 kg adult, at the lower 5 g/kg limit, 350 g could produce death in humans. For comparison's sake, the LD₅₀ of salt is reported to be 3.75 g/kg in rats according to the Merck Index. According to the Agency for Toxic Substances and Disease Registry, "The minimal lethal dose of ingested boron (as boric acid) was reported to be 2–3 g in infants, 5–6 g in children, and 15–20 g in adults. [...] However, a review of 784 human poisonings with boric acid (10–88 g) reported no fatalities, with 88% of cases being asymptomatic."<ref name=HHS2010/> Human studies in three borate exposure-rich comparison groups (U.S. Borax mine and production facility workers, Chinese boron workers, Turkish residents living near boron-rich regions) produced no indicators of developmental toxicity in blood and semen tests. The highest estimated exposure was 5 mg B/kg/day, likely due to eating in contaminated workplaces, more than 100 times the average daily exposure.<ref name=CLH2018/>

Long-term exposure to boric acid may be of more concern, causing kidney damage and eventually kidney failure (see links below). Although it does not appear to be carcinogenic, studies in dogs have reported testicular atrophy after exposure to 32 mg/(kg⋅day) for 90 days. This level, were it applicable to humans at like dose, would equate to a cumulative dose of 202 g over 90 days for a 70 kg adult, not far lower than the above LD₅₀.<ref name=FQPA2006/>

According to the CLH report for boric acid published by the Bureau for Chemical Substances Lodz, Poland, boric acid in high doses shows significant developmental toxicity and teratogenicity in rabbit, rat, and mouse fetuses, as well as cardiovascular defects, skeletal variations, and mild kidney lesions.<ref name=CLH2018/> As a consequence in the 30th ATP to EU directive 67/548/EEC of August 2008, the European Commission decided to amend its classification as reprotoxic category 2 and to apply the risk phrases R60 (may impair fertility) and R61 (may cause harm to the unborn child).<ref name=BYU2008/><ref name=ishii1993/><ref name=rest1992/><ref name=duld2009/><ref name=NSWFA2009/>

At a 2010 European Diagnostics Manufacturing Association (EDMA) Meeting, several new additions to the substance of very high concern (SVHC) candidate list in relation to the Registration, Evaluation, Authorisation and Restriction of Chemicals Regulations 2007 (REACH) were discussed. Following the registration and review completed as part of REACH, the classification of boric acid CAS 10043-35-3 / 11113-50-1 is listed from 1 December 2010 is H360FD (May damage fertility. May damage the unborn child).<ref name=ECHA2010/><ref name=EUP2008/>

Physics

Sound absorption in oceans not only depends on water molecules but also on dissolved salts present in low concentration in seawater.<ref name="NPL2018" /><ref name="Ainslie1998"/> Boric acid and borate Template:Nowrap in seawater)<ref name="Byrne2024" /> relaxation contributes to absorbing sounds in the low‐frequency region (0.2–10 kHz).<ref name="Francois1982_Part_II" /> At higher frequencies, between 10 and 1000 kHz magnesium sulfate (formed by the second most abundant cation and anion species in seawater) is the main contributor to the absorption of acoustic waves in seawater.<ref name="Francois1982_Part_I" />

Uses

Industrial

The primary industrial use of boric acid is in the manufacture of monofilament fiberglass, which is usually referred to as textile fiberglass. Textile fiberglass is used to reinforce plastics in applications that range from boats to industrial piping to computer circuit boards.<ref name=kist1994/>

In the jewelry industry, boric acid is often used in combination with denatured alcohol to reduce surface oxidation and formation of firescale on metals during annealing and soldering operations.<ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Boric acid is used in the production of glass in LCD flat panel displays.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite magazine</ref>

In electroplating, boric acid is used as part of some proprietary formulas. One known formula uses about a 1 to 10 ratio of Template:Chem to [[nickel(II) sulfate|Template:Chem]], a very small portion of sodium lauryl sulfate and a small portion of [[sulfuric acid|Template:Chem]].

The solution of orthoboric acid and borax in 4:5 ratio is used as a fire retarding agent of wood by impregnation.<ref name=tsuy2009/> Also, it is used in combination with other chemicals for the fire retardancy of wood-based materials.<ref>Template:Cite journal</ref>

It is also used in the manufacturing of ramming mass, a fine silica-containing powder used for producing induction furnace linings and ceramics.

Boric acid is added to borax for use as welding flux by blacksmiths.<ref name=demp2010/>

Boric acid, in combination with polyvinyl alcohol (PVA) or silicone oil, is used to manufacture Silly Putty.<ref name=silly2013/>

Boric acid is also present in the list of chemical additives used for hydraulic fracturing (fracking) in the Marcellus Shale in Pennsylvania.<ref name=PDEP2010/> It is often used in conjunction with guar gum as cross-linking and gelling agent for controlling the viscosity and the rheology of the fracking fluid injected at high pressure in the well. It is important to control the fluid viscosity for keeping in suspension on long transport distances the grains of the propping agents aimed at maintaining the cracks in the shales sufficiently open to facilitate the gas extraction after the hydraulic pressure is relieved.<ref name=fink2015/><ref name=bish2004/><ref name=EUP3004279/> The rheological properties of borate cross-linked guar gum hydrogel mainly depend on the pH value.<ref name=wang2016/>

Boric acid is used in some expulsion-type electrical fuses as a de-ionization/extinguishing agent.<ref>Template:Cite book</ref> During an electrical fault in an expulsion-type fuse, a plasma arc is generated by the disintegration and rapid spring-loaded separation of the fusible element, which is typically a specialized metal rod that passes through a compressed mass of boric acid within the fuse assembly. The high-temperature plasma causes the boric acid to rapidly decompose into water vapor and boric anhydride, and in-turn, the vaporization products de-ionize the plasma, helping to interrupt the electrical fault.<ref>Template:Cite journal</ref>

Medical

Boric acid can be used as an antiseptic for minor burns or cuts and is sometimes used in salves and dressings, such as boracic lint. Boric acid is applied in a very dilute solution as an eye wash. Boric acid vaginal suppositories can be used for recurrent candidiasis due to non-albicans candida as a second line treatment when conventional treatment has failed.<ref name="iava2010" /><ref name=aber2010/> It is less effective than conventional treatment overall.<ref name="iava2010" /> Boric acid largely spares lactobacilli within the vagina.<ref name=sobel2021/> As TOL-463, it is under development as an intravaginal medication for the treatment for vulvovaginal candidiasis.<ref name=adisTOL463/><ref name=nyir2022/><ref name=marra2019/>

As an antibacterial compound, boric acid can also be used as an acne treatment. It is also used as a prevention of athlete's foot, by inserting powder in the socks or stockings. Various preparations can be used to treat some kinds of {{#invoke:Lang|lang}} (ear infection) in both humans and animals.<ref name="adriz2018" /> The preservative in urine sample bottles in the UK is boric acid.<ref>Template:Cite book</ref>

Boric acid solutions used as an eye wash or on abraded skin are known to be toxic, particularly to infants, especially after repeated use; this is because of its slow elimination rate.<ref name=harv1980/>

Boric acid is one of the most commonly used substances that can counteract the harmful effects of reactive hydrofluoric acid (HF) after accidental contact with the skin. It works by forcing the free Template:Chem2 anions into the inert tetrafluoroborate anion. This process defeats the extreme toxicity of hydrofluoric acid, particularly its ability to sequester ionic calcium from blood serum which can lead to cardiac arrest and bone decomposition; such an event can occur from just minor skin contact with HF.<ref name=EPA2015/>Template:Failed verification

Insecticidal

Boric acid was first registered in the US as an insecticide in 1948 for control of cockroaches, termites, fire ants, fleas, silverfish, and many other insects. The product is generally considered safe in household kitchens to control cockroaches and ants. It acts as a stomach poison affecting the insects' metabolism. The dry powder is abrasive to the insects' exoskeletons.<ref name=ABC/><ref name=boone/><ref name=REDF2022/> It is in non-specific IRAC group 8D. Boric acid is also known as "the gift that keeps on killing" because cockroaches cross over lightly dusted areas and do not die immediately. Still, the effect is like shards of glass cutting them apart. This often allows a cockroach to return to the nest, where it soon dies. Cockroaches, being cannibalistic, eat others killed by contact or consumption of boric acid, consuming the powder trapped in the dead roach and killing them, too.Template:Citation needed

Boric acid is also widely used in wood treatment to protect against termites. The full complexity of its mechanism is not fully understood. Still, aside from causing dose-dependent mortality, boric acid causes dysbiosis in the Eastern Subterranean termite, leading to the opportunistic rise of insect pathogens that could be contributing to mortality.<ref>Template:Cite journal</ref> In Japan the practice of laying newspapers treated with o-boric acid and borax under buildings has been effective in controlling Coptotermes formosanus and Reticulitermes speratus populations. Decaying wood treated with 0.25 to 0.5 percent disodium octaborate (Template:Chem2, commonly abbreviated DOT) is also effective for baiting Heterotermes aureus populations. A 1997 paper concluded: "Borate baits would undoubtedly be helpful in the long-term, but do not appear sufficient as a sole method of structural protection."<ref>Template:Cite journal</ref>

Preservation

In combination with its use as an insecticide, boric acid also prevents and destroys existing wet and dry rot in timbers. It can be used in combination with an ethylene glycol carrier to treat external wood against fungal and insect attack. It is possible to buy borate-impregnated rods for insertion into wood via drill holes where dampness and moisture are known to collect and sit. It is available in a gel form and injectable paste form for treating rot-affected wood without replacing the timber. Concentrates of borate-based treatments can be used to prevent slime, mycelium, and algae growth, even in marine environments.Template:Citation needed

Boric acid is added to salt in the curing of cattle hides, calfskins, and sheepskins. This helps to control bacterial development and insects.Template:Citation needed

pH buffer

File:Borate pH.gif

Boric acid predominates in solution below pH 9

File:Borate buffer.gif

Boric acid buffers against rising pH in swimming pools

Boric acid in equilibrium with its conjugate base the borate ion is widely used (in the concentration range 50–100 ppm boron equivalents) as a primary or adjunct pH buffer system in swimming pools. Boric acid is a weak acid, with pK_a (the pH at which buffering is strongest because the free acid and borate ion are in equal concentrations) of 9.24 in pure water at 25 °C. But apparent pK_a is substantially lower in swimming pool or ocean waters because of interactions with various other molecules in solution. It will be around 9.0 in a saltwater pool. No matter which form of soluble boron is added, within the acceptable range of pH and boron concentration for swimming pools, boric acid is the predominant form in aqueous solution, as shown in the accompanying figure. The boric acid – borate system can be useful as a primary buffer system (substituting for the bicarbonate system with pK_a1 = 6.0 and pK_a2 = 9.4 under typical salt-water pool conditions) in pools with salt-water chlorine generators that tend to show upward drift in pH from a working range of pH 7.5–8.2. Buffer capacity is greater against rising pH (towards the pKa around 9.0), as illustrated in the accompanying graph. The use of boric acid in this concentration range does not allow any reduction in free HOCl concentration needed for pool sanitation. Still, it may add marginally to the photo-protective effects of cyanuric acid and confer other benefits through anti-corrosive activity or perceived water softness, depending on overall pool solute composition.<ref name=birch2013/>

Lubrication

Colloidal suspensions of nanoparticles of boric acid dissolved in petroleum or vegetable oil can form a remarkable lubricant on ceramic or metal surfaces<ref name=duzc2009/> with a coefficient of sliding friction that decreases with increasing pressure to a value ranging from 0.10 to 0.02. Self-lubricating Template:Chem2 films result from a spontaneous chemical reaction between water molecules and Template:Chem2 coatings in a humid environment. On a bulk scale, an inverse relationship exists between the friction coefficient and the Hertzian contact pressure induced by the applied load.Template:Citation needed

Boric acid is used to lubricate carrom and novuss boards, allowing for faster play.<ref name=singh2009/>

Nuclear power

Boric acid is used in some nuclear power plants as a neutron poison. The boron in boric acid reduces the probability of thermal fission by absorbing some thermal neutrons. Fission chain reactions are generally driven by the probability that free neutrons will result in fission and is determined by the material and geometric properties of the reactor. Natural boron consists of approximately 20% boron-10 and 80% boron-11 isotopes. Boron-10 has a high cross-section for absorption of low-energy (thermal) neutrons. By increasing boric acid concentration in the reactor coolant, the probability that a neutron will cause fission is reduced. Changes in boric acid concentration can effectively regulate the rate of fission taking place in the reactor. During normal at power operation, boric acid is used only in pressurized water reactors (PWRs), whereas boiling water reactors (BWRs) employ control rod pattern and coolant flow for power control. However, BWRs can use an aqueous solution of boric acid and borax or sodium pentaborate for an emergency shutdown system if the control rods fail to insert. Boric acid may be dissolved in spent fuel pools used to store spent fuel elements. The concentration is high enough to keep neutron multiplication at a minimum. Boric acid was dumped over Reactor 4 of the Chernobyl nuclear power plant after its meltdown to prevent another reaction from occurring.Template:Citation needed

Pyrotechnics

Boron is used in pyrotechnics to prevent the amide-forming reaction between aluminium and nitrates. A small amount of boric acid is added to the composition to neutralize alkaline amides that can react with the aluminium.

Boric acid can be used as a colorant to make fire green. For example, when dissolved in methanol, it is popularly used by fire jugglers and fire spinners to create a deep green flame much stronger than copper sulfate.<ref name=weing1947/>

Agriculture

Boric acid is used to treat or prevent boron deficiencies in plants. It is also used in the preservation of grains such as rice and wheat.<ref name=CFS2019/>

References

<references> <ref name="webster">Entry "boracic acid" in the online Merriamm-Webster Dictionary. Gives the first use as 1790. Retrieved 2022-06-24.</ref> <ref name="eisler2007">Template:Cite book</ref> <ref name="balci2012">Template:Cite journal</ref> <ref name="jolly1984">Template:Cite book</ref> <ref name="JEE2014">Template:Cite book</ref> <ref name="darp2000">Template:Cite book</ref> <ref name="NIST1969">Template:Cite book</ref> <ref name="rota2017">Andrei Rotaru (2017): "Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow." Journal of Thermal Analysis and Calorimetry, volume 127, pages 755–763. {{#invoke:doi|main}}</ref> <ref name="brown1956">Template:Cite journal</ref> <ref name="ncbi">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="chemsrc">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="hous2008">Template:Cite book</ref> <ref name="hous2005">Template:Cite book</ref> <ref name="tsuy2007">Template:Cite journal</ref> <ref name="tsuy2009">Template:Cite journal</ref> <ref name="GandE">Template:Greenwood&Earnshaw</ref> <ref name="vogelP357">Template:VogelQuantitative6th</ref> <ref name="HHS2010">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="FQPA2006">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="CLH2018">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="BYU2008">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="ishii1993">Template:Cite journal</ref> <ref name="rest1992">Template:Cite journal</ref> <ref name="duld2009">Template:Cite encyclopedia</ref> <ref name="NSWFA2009">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="ECHA2010">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="EUP2008">Regulation (EC) No 1272/2008 of the European Parliament and of the Council, 16 December 2008</ref> <ref name="kist1994">Template:Cite book</ref> <ref name="demp2010">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="silly2013">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="PDEP2010">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="fink2015">Template:Cite book</ref> <ref name="bish2004">Template:Cite journal</ref> <ref name="EUP3004279">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="wang2016">Template:Cite journal</ref> <ref name="aber2010">Template:Cite book</ref> <ref name="iava2010">Template:Cite journal</ref> <ref name="sobel2021">Template:Cite journal</ref> <ref name="adisTOL463">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="nyir2022">Template:Cite journal</ref> <ref name="marra2019">Template:Cite journal</ref> <ref name="adriz2018">Template:Cite journal</ref> <ref name="harv1980">Template:Cite book</ref> <ref name="EPA2015">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="ABC">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="boone">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="REDF2022">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="birch2013">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="duzc2009">Template:Cite journal</ref> <ref name="singh2009">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="weing1947">Template:Cite book</ref> <ref name="CFS2019">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="kaur2021">Gurwinder Kaur, Shagun Kainth, Rohit Kumar, Piyush Sharma and O. P. Pandey (2021): "Reaction kinetics during non-isothermal solid-state synthesis of boron trioxide via boric acid dehydration." Reaction Kinetics, Mechanisms and Catalysis, volume 134, pages 347–359. {{#invoke:doi|main}}</ref> <ref name="aghi2018">Siavash Aghili, Masoud Panjepour, and Mahmood Meratian (2018): "Kinetic analysis of formation of boron trioxide from thermal decomposition of boric acid under non-isothermal conditions." Journal of Thermal Analysis and Calorimetry, volume 131, pages 2443–2455. {{#invoke:doi|main}}</ref> <ref name="tachi2004">Masanori Tachikawa (2004): "A density functional study on hydrated clusters of orthoboric acid, B(OH)₃(H₂O)_n (n=1–5)". Journal of Molecular Structure: THEOCHEM, volume 710, issues 1–3, pages 139-150. {{#invoke:doi|main}}</ref> <ref name="Belcher1960">Template:Cite book</ref> <ref name="NPL2018">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> <ref name="Ainslie1998">Template:Cite journal</ref> <ref name="Francois1982_Part_II">Template:Cite journal</ref> <ref name="Francois1982_Part_I">Template:Cite journal</ref> <ref name="Byrne2024">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> </references>

Further reading

• Template:Cite book
• Template:Cite book
• Cordia, J.A., Bal, E.A., Mak, W.A. and Wils, E.R.J. (2003). Determination of some physico-chemical properties of Optibor EP. Rijswijk, The Netherlands: TNO Prins Maurits Laboratory, report PML 2002-C42rr, GLP, Unpublished, confidential data provided by Borax Europe Limited.

External links

• Template:Commons category-inline
• Boric Acid Technical Fact Sheet – National Pesticide Information Center
• Boric Acid General Fact Sheet – National Pesticide Information Center
• International Chemical Safety Card 0991
• US EPA Pesticide Reregistration Eligibility Decision
• National Pollutant Inventory – Boron and compounds
• Boric acid at ChemicalLand21
• European Chemicals Agency (ECHA) "New Public Consultation on Eight Potential Substances of Very High Concern" – includes Boric Acid. Closes 22 April 2010
• ChemSub Online: Boric acid