Boric Acid - Overview, Structure, Preparation, Uses, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:26 PM IST

Boric acid chemical formula H₃BO₃ and it is a monobasic Lewis acid. It is usually found in powder form. The boric acid powder is also called hydrogen borate, boracic acid, Actium Boricua, or Orthoboric Acid, Antiviral, antifungal, and antiseptic properties make this an effective acid. There is no particular smell associated with boric acid powder since it is soluble in water. A white powdery compound may also exist under standard conditions.

This Story also Contains

Medicines containing Boric acid
The structure of molecules and crystals
Boric acid preparation
Poisoning by Boric acid

Boric Acid - Overview, Structure, Preparation, Uses, FAQs

Drying Boric Acid

Medicines containing Boric acid

A common use of boric acid in the treatment of minor cuts and burns is as an antiseptic. In addition to its use in dressings and salves, this compound is also used in medicine. You can use boric acid as an eyewash at very dilute concentrations. Humans can also treat acne with boric acid because of its antibacterial properties. It can be found in powdered form. Additionally, it can be sprinkled in socks and shoes to prevent athlete's

Consuming or inhaling excessive amounts of boric acid can lead to poisoning. Boric acid can also seriously damage the kidneys after prolonged exposure.

The structure of molecules and crystals

A trigonal planar geometry of oxygen atoms surrounds the boron. O-H is 97 pm long, while B-O is 136 cm long. There are three molecular point groups in the molecule.

B(OH)₃ molecules arranged in layers in crystallized boric acid are linked by hydrogen bonds of 272 micrometres in length. Three hundred eighty-six pixels separate two adjacent layers.

Structure of boric acid

Boric acid preparation

Making boric acid is relatively easy when you combine Borax with any mineral acid (such as hydrogen chloride). For this reaction, you can write the following chemical equation:

Na₂B₄O₇.10H₂O + 2HCl → 4H₃BO₃ + 5H₂O + 2NaCl

The hydrolysis of Diborane or trihalides of boron can also result in the production of boric acid (such as boron trichloride or boron trifluoride).

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Boric acid - H₃BO₃ Properties

H3BO3	Boric acid
Molar Mass/Molecular Weight	61.83 g·mol⁻¹
Density	1.435 g/cm³
Boiling Point	158 °C
Melting Point	300 °C

As a crystalline solid, boric acid is soluble in water under standard conditions of temperature and pressure (STP). It is temperature-dependent how well H₃BO₃ dissolves in water. Solubility is 57 grams per liter of boric acid in water at a temperature of 25 degrees Celsius. This compound is, however, soluble in water when heated to 100 degrees Celsius, where its solubility increases to approximately 275 grams per liter.

Furthermore, boric acid is only slightly soluble in acetone and barely soluble in pyridine. An ion of boric acid is called the borate anion as its conjugate base.

Boric acid solutions are acidic when containing polyols containing cis-vicinal diols (for example, mannitol and glycerol). Under different concentrations of mannitol, pK of B(OH)₃ has been found to vary by five orders of magnitude (from 9 to 4). As a result, boric acid with increased acidity can be called magnetologic acid in presence of mannitol.

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H₃BO₃ Molecule Structure

Boric acid molecules are composed of single bonds between boron and oxygen. Three hydroxyl groups surround the boron atom and link it to the central position. Overall, boric acid has a triangular planar molecular geometry. This is a diagram illustrating how H₃BO₃ molecules are structured.

How is Boric acid Used?

Boric acid is used for the following purposes.

Fiberglass textiles are made with it

Inflatable displays are made from this material
In hydrofluoric acid, it neutralizes the active acids.
A blacksmith uses it to make welding flux
The electroplating process uses this.
Jewellery manufacturers use it.
Silly putty is made from it
Insecticidal properties.
Antiseptic and antibacterial properties make it useful.
As a dry lubricant, it is used on carrom boards.
Some nuclear plants use it as a neutron poison
It preserves grains like wheat and rice.
Boric powder for cockroaches is best for pest control.

The use of boric acid is not uncommon when it comes to the list of chemical additives included in hydraulic fracturing (also known as fracking). Furthermore, it is also used as a cross-linking and gelling agent in the drilling fluid, which is pumped at high pressure into wells, so that its viscosity and rheology can be regulated.

Moreover, it is essential to regulate the fluid viscosity in order to keep the grains of the propping agents suspended for long distances during transportation, as well as to keep the cracks in the shales open for gas extraction after relieving the hydraulic pressure.

Poisoning by Boric acid

Chronic or acute poisoning from this substance is possible. The effects of acute boric acid poisoning are similar to those of roach-killing powders. When ingested in large quantities, boric acid can cause serious damage to many areas of the body. It may take several weeks for the damage to the esophagus and stomach to resolve after swallowing boric acid. Death may result from complications that manifest months after the initial diagnosis.

Studies have shown that exposure to borax did not cause long-term respiratory problems. However, boric acid is linked to gastrointestinal discomfort over the long term. Common side effects include headaches, fever, tremors, twitching, lack of energy, and weakness. There have been varying limits to the use of borax in insecticides in the United States since 1946. Borax was abolished from all EPA limits in February 1986 due to its low toxicity, according to two EPA records.

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Frequently Asked Questions (FAQs)

1. What is the solubility of boric acid in acetone?

It is crippling to consume boric acid. Liquid ammonia is soluble in acetone, glycerol, ether, alcohol, and methanol, but only partially soluble in acetone in water. Sodium borate or halides of boron can be hydrolysed to form boric acid. Boron oxide crystals are somewhat soluble in cold water and somewhat soluble in hot water.

2. What is the purpose of boric acid?

Among its numerous chemical applications are antiseptics, insecticides, flame retardants, neutron absorbents, and precursors.

3. Why does boric acid need to be neutralized?

Acid and base are damaged by neutralization because their acidic properties and fundamental properties are altered. Acids can be neutralized with lime and baking soda, which are both readily available chemicals.

4. Boric acid: what is it exactly?

In addition to being an antiseptic, insecticide, flame retardant, neutron absorbent, and precursor to other chemical compounds, boronic acid is also known as hydrogen borate, boracic acid, orthoboric acid, or acid Boricua.

5. Q5. What is boric acid used for?

Boric acid serves as an excellent cleaner for all types of mold problems and insects such as ants, cockroaches, silverfish, fleas, and others.

6. Can boric acid be used in gardening?

Yes, boric acid can be beneficial in gardening to combat pests. Additionally, it may help with fungal diseases. However, care should be taken to apply it judiciously, as excessive use can harm beneficial insects and the soil ecosystem.

7. How is boric acid prepared industrially?

Boric acid is typically prepared industrially by reacting borax (sodium tetraborate) with a strong acid like hydrochloric acid. The reaction produces boric acid and sodium chloride. Another method involves the reaction of boron minerals with sulfuric acid.

8. What is boric acid and why is it considered a Lewis acid?

Boric acid (H3BO3) is a weak acid derived from boron. It's considered a Lewis acid because it can accept an electron pair from a base, forming a coordinate covalent bond. This behavior is due to the empty p-orbital on the boron atom, which can accept electrons.

9. How does boric acid interact with water molecules?

In water, boric acid doesn't dissociate like typical acids. Instead, it accepts a hydroxide ion from water, forming a tetrahedral borate anion [B(OH)4]- and releasing a proton. This reaction is the basis for its weak acidic behavior in aqueous solutions.

10. Why is boric acid considered a weak acid despite having three hydrogen atoms?

Boric acid is a weak acid because it doesn't readily donate protons in aqueous solution. Instead, it acts as a Lewis acid, accepting OH- ions from water molecules. This results in a lower concentration of H+ ions in solution compared to strong acids.

11. How does the presence of boric acid affect the pH of a solution?

Boric acid only slightly lowers the pH of a solution due to its weak acidic nature. In water, it forms a buffer system with its conjugate base, the borate ion. This buffer system helps maintain a relatively stable pH even with small additions of strong acids or bases.

12. How does boric acid function as an antiseptic?

Boric acid acts as a mild antiseptic by disrupting the cell membranes of microorganisms. It also creates an acidic environment that inhibits bacterial growth. However, its effectiveness is limited compared to modern antiseptics, and it's mainly used for specific applications.

13. Why is boric acid used in contact lens solutions?

Boric acid is used in contact lens solutions as a pH buffer and mild antiseptic. It helps maintain a pH compatible with the eye's natural environment and provides some protection against microbial growth, enhancing the overall effectiveness of the cleaning solution.

14. How does boric acid interact with amino acids and proteins?

Boric acid can form complexes with certain amino acids and proteins, particularly those containing hydroxyl groups. This interaction can affect protein structure and function. In some cases, this property is exploited in biochemical research or in the development of boron-based drugs.

15. What is the relationship between boric acid and boron deficiency in plants?

Boric acid is a common source of boron for plants suffering from boron deficiency. Boron is an essential micronutrient for plant growth, involved in cell wall formation and reproductive processes. Boric acid can be applied as a soil amendment or foliar spray to correct boron deficiency in crops.

16. What is the significance of boric acid in organic synthesis?

Boric acid is used in organic synthesis as a mild acid catalyst. It can catalyze esterification reactions and certain condensation reactions. Its Lewis acidic nature makes it useful for activating carbonyl compounds and in some cases, protecting group chemistry.

17. What is the environmental impact of boric acid?

Boric acid has a relatively low environmental impact when used properly. It's not highly toxic to mammals but can be harmful to aquatic organisms in high concentrations. It doesn't persist in the environment for long periods and doesn't bioaccumulate significantly in food chains.

18. Why is boric acid sometimes used in food preservation?

Boric acid has been used as a food preservative due to its antimicrobial properties. It inhibits the growth of yeasts, molds, and bacteria. However, its use in food is now restricted or banned in many countries due to potential health concerns associated with long-term consumption.

19. How does boric acid contribute to flame retardancy in materials?

Boric acid acts as a flame retardant by forming a protective layer of char when heated. This char layer insulates the material beneath, slowing down combustion. Additionally, boric acid releases water vapor when heated, which helps to cool the burning material and dilute flammable gases.

20. What role does boric acid play in nuclear power plants?

Boric acid is used in nuclear power plants as a neutron absorber. It's added to the coolant water to control the nuclear fission rate in the reactor core. The boron atoms in boric acid effectively capture neutrons, helping to regulate the chain reaction.

21. How does boric acid behave in non-aqueous solvents?

In non-aqueous solvents, boric acid's behavior can differ from its aqueous chemistry. In some organic solvents, it may exhibit stronger acidic properties due to the lack of competing water molecules. Its solubility and reactivity in non-aqueous media depend on the specific solvent properties and potential for hydrogen bonding.

22. How does the structure of boric acid contribute to its properties?

Boric acid has a planar triangular structure with three hydroxyl groups attached to the central boron atom. This structure allows for hydrogen bonding between molecules, contributing to its relatively low melting point and its ability to form sheets in its solid form.

23. What is the difference between orthoboric acid and metaboric acid?

Orthoboric acid (H3BO3) is the common form of boric acid with three hydroxyl groups. Metaboric acid (HBO2) is formed when boric acid is heated, losing one water molecule. Metaboric acid exists as a cyclic trimer (H3B3O6) in the solid state.

24. How does boric acid compare to borax in terms of chemical properties?

Boric acid (H3BO3) is a weak acid, while borax (Na2B4O7·10H2O) is a salt that forms a basic solution in water. Boric acid has a simpler molecular structure, while borax contains a complex borate anion. Both compounds contain boron, but they behave differently in chemical reactions due to their distinct structures.

25. How does boric acid interact with other elements in the periodic table?

As a boron compound, boric acid exhibits typical p-block element behavior. It can form complexes with various metals and act as a Lewis acid with electron-rich species. Its reactivity is influenced by the empty p-orbital on boron, allowing it to form both covalent and coordinate covalent bonds.

26. How does boric acid behave at high temperatures?

When heated, boric acid undergoes dehydration in stages. First, it forms metaboric acid (HBO2) at around 170°C. Further heating leads to tetraboric acid (H2B4O7) and eventually to boron trioxide (B2O3) at temperatures above 300°C. This behavior is important in its applications as a flux and in ceramics.

27. Why is boric acid used in the manufacture of fiberglass?

Boric acid is used in fiberglass production because it acts as a fluxing agent, lowering the melting point of the glass mixture. It also helps to control the viscosity of the molten glass and improves the chemical resistance of the final product.

28. What is the role of boric acid in the production of borosilicate glass?

In borosilicate glass production, boric acid (or its anhydride, boron trioxide) is a crucial component. It increases the glass's resistance to thermal shock, improves its durability, and enhances its chemical resistance. The boron atoms become part of the glass network, modifying its properties.

29. How does boric acid behave in supercritical fluids?

In supercritical fluids, particularly supercritical water, boric acid's behavior can be quite different from its behavior under normal conditions. The unique properties of supercritical fluids can enhance the solubility and reactivity of boric acid, which is relevant in some industrial processes and in understanding geochemical phenomena.

30. How does boric acid contribute to the properties of ceramic glazes?

In ceramic glazes, boric acid (usually added as its anhydride, B2O3) acts as a flux and a glass former. It l

31. What is the significance of boric acid in geochemistry?

In geochemistry, boric acid and its salts play important roles. They are found in certain mineral deposits and can be indicators of past geological processes. Boric acid's behavior in hydrothermal systems and its incorporation into minerals provide insights into geological formations and environmental conditions.

32. How does boric acid contribute to the hardness of water?

Boric acid itself doesn't significantly contribute to water hardness. However, borates (the salts of boric acid) can contribute to temporary water hardness. This is less common than hardness caused by calcium and magnesium ions, but it can occur in some geological settings rich in boron minerals.

33. What is the role of boric acid in the production of boron-based semiconductors?

Boric acid is a precursor in the production of boron-based semiconductors. It can be reduced to elemental boron, which is then used to dope silicon or other semiconductor materials. The precise control of boron concentration is crucial for tailoring the electrical properties of these semiconductors.

34. What is the significance of boric acid in analytical chemistry?

In analytical chemistry, boric acid is used in various ways. It can act as a buffer in certain pH ranges, as a complexing agent for some metal ions, and in the preparation of standard solutions. Its ability to form esters with alcohols is also used in some analytical procedures.

35. How does boric acid contribute to the flame color in fireworks?

Boric acid, when heated in a flame, produces a characteristic green color. This is due to the electronic transitions of boron atoms in the gas phase. This property is utilized in fireworks and flame tests, where boric acid or its salts are used to produce green flames.

36. What is the role of boric acid in the production of boron carbide?

Boric acid is a key starting material in the production of boron carbide (B4C), one of the hardest materials known. The process typically involves the reduction of boric acid with carbon at high temperatures. This reaction produces boron carbide, which is used in abrasives and armor materials.

37. How does boric acid affect the melting point of other substances?

Boric acid often acts as a flux, lowering the melting point of other substances. This property is utilized in metallurgy and ceramics. When mixed with other compounds, boric acid can form eutectic mixtures with lower melting points than either component alone, facilitating processes like soldering and glazing.

38. What is the significance of boric acid in the context of green chemistry?

In green chemistry, boric acid is considered a relatively benign substance. It's non-volatile, non-flammable, and biodegradable. Its use as a mild acid catalyst in organic synthesis aligns with green chemistry principles by potentially reducing the need for stronger, more hazardous acids in some reactions.

39. What is the role of boric acid in the production of sodium borohydride?

Boric acid is a starting material in the production of sodium borohydride (NaBH4), a powerful reducing agent. The process involves the reaction of boric acid with sodium hydride under controlled conditions. This illustrates how boric acid can be transformed into more reactive boron compounds.

40. How does boric acid interact with cellulose and other polysaccharides?

Boric acid can form complexes with cellulose and other polysaccharides containing vicinal diol groups. This interaction can affect the properties of these materials, such as their solubility and rheological behavior. This property is relevant in paper manufacturing and some food applications.

41. What is the significance of boric acid in the context of boron neutron capture therapy?

Boric acid and its derivatives are of interest in boron neutron capture therapy (BNCT), an experimental cancer treatment. The principle relies on the high neutron capture cross-section of boron-10. Compounds derived from boric acid are being researched as potential agents for selectively delivering boron to tumor cells.

42. How does boric acid contribute to the properties of borax glass?

When borax is heated, it loses water and forms a glassy substance. The presence of boric acid (or its anhydride) in this glass affects its properties. It lowers the melting point, increases the glass's resistance to thermal shock, and modifies its optical properties. This is the basis for borax bead tests in qualitative analysis.

43. What is the role of boric acid in the formation of organoboron compounds?

Boric acid is a precursor in the synthesis of various organoboron compounds. It can react with organic compounds, particularly alcohols, to form borate esters. These esters are intermediates in the production of more complex organoboron compounds, which have significant applications in organic synthesis and materials science.

44. How does boric acid behave in extreme pH conditions?

In strongly acidic conditions, boric acid remains largely undissociated. In strongly basic conditions, it forms various borate anions, with the exact species depending on the pH and concentration. At very high pH, the predominant species is the tetraborate ion, [B4O5(OH)4]2-. Understanding this behavior is crucial in many industrial and environmental applications.

45. What is the significance of boric acid in the context of isotope geochemistry?

Boric acid and its salts are important in isotope geochemistry, particularly in studying the boron isotope system. The ratio of boron-10 to boron-11 in boric acid and borates can provide information about past environmental conditions, such as ocean pH, and is used in paleoclimate studies.

46. How does boric acid affect the properties of polymers when used as an additive?

When used as an additive in polymers, boric acid can act as a flame retardant and can modify the mechanical and thermal properties of the polymer. It can form crosslinks between polymer chains, potentially increasing the material's strength and heat resistance. However, its effectiveness and impact depend on the specific polymer system.

47. What is the role of boric acid in the production of elemental boron?

Boric acid is a common starting material for producing elemental boron. One method involves the reduction of boric acid with magnesium or sodium at high temperatures. Another approach is the electrolysis of molten borax, where boric acid is an intermediate. These processes illustrate the central role of boric acid in boron chemistry.

48. How does boric acid contribute to the properties of optical fibers?

In optical fiber production, boric acid or its derivatives are used as dopants in the silica glass. The addition of boron modifies the refractive index of the glass, which is crucial for controlling the light-guiding properties of the fiber. It also affects the fiber's thermal and mechanical characteristics.

49. What is the significance of boric acid in geothermal energy systems?

In geothermal energy systems, boric acid can be present in geothermal fluids. Its presence can affect the chemistry of these fluids, potentially leading to scaling or corrosion issues in geothermal power plants. Understanding and managing boric acid chemistry is important for the efficient operation of these systems.

50. How does boric acid interact with transition metal complexes?

Boric acid can interact with transition metal complexes in various ways. It can act as a ligand, forming coordinate bonds with metal ions. In some cases, it can modify the properties of metal complexes, affecting their reactivity, solubility, or spectroscopic characteristics. This behavior is relevant in both inorganic chemistry research and certain industrial processes.

51. What is the role of boric acid in the production of boron nitride?

Boric acid is a key precursor in the production of boron nitride (BN). One common method involves reacting boric acid with ammonia or urea at high temperatures. This process demonstrates how boric acid can be transformed into advanced ceramic materials with unique properties, such as high thermal conductivity and electrical insulation.

52. How does boric acid behave in molten salt systems?

In molten salt systems, boric acid (or more commonly, its anhydride B2O3) can act as a network former or modifier, depending on the composition of the salt mixture. It can affect the melting point, viscosity, and other physical properties of the molten salt. This behavior is relevant in applications such as molten salt reactors and certain metallurgical processes.

53. What is the significance of boric acid in the context of soil chemistry?

In soil chemistry, boric acid plays a role in boron availability for plants. Its behavior in soil is influenced by factors such as pH, organic matter content, and the presence of other minerals. Understanding boric acid's interactions in soil is crucial for managing boron nutrition in agriculture and for studying boron's environmental cycling.