Boric acid

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Application of Boric acid

Industrial

  • The primary industrial use of boric acid is in the manufacture of monofilament fiberglass 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.
  • In the jewelry industry, boric acid is often used in combination with denatured alcohol to reduce surface oxidation and firescale from forming on metals during annealing and solderingoperations.
  • Boric acid is used in the production of the glass in LCD flat panel displays.
  • In electroplating, boric acid is used as part of some proprietary formulas. One such known formula calls for about a 1 to 10 ratio of H
    Boric acid, mixed with borax (sodium tetraborate decahydrate) at the weight ratio of 4:5, is highly soluble in water, though they are not so soluble separately. The solution is used for fire retarding agent of wood by impregnation.
  • 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 one of the most commonly used substances that can neutralize active hydrofluoric acid (HF). It works by forcing the free F anions into complex salts. 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.
  • Boric acid is added to borax for use as welding flux by blacksmiths.
  • Boric acid, in combination with silicone oil, is used to manufacture Silly Putty.
  • Boric acid may be used in Marcellus Shale hydraulic fracturing in Pennsylvania.

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. Dilute boric acid can be used as a vaginal douche to treat bacterial vaginosis due to excessive alkalinity,[28] as well as candidiasis due to non-albicans candida.[29] As an antibacterial compound, boric acid can also be used as an acne treatment. It is also used as prevention of athlete's foot, by inserting powder in the socks or stockings, and in alcohol solution can be used to treat some kinds of otitis externa (ear infection) in both humans and animals. The preservative in urine sample bottles in the UK is boric acid.
  • 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.

Insecticidal

  • Boric acid was first registered in the US as an insecticide in 1948 for control of cockroachestermitesfire antsfleassilverfish, and many other insects. The product is generally considered to be safe to use in household kitchens to control cockroaches and ants. It acts as a stomach poison affecting the insects' metabolism, and the dry powder is abrasiveto the insects' exoskeletons. Boric acid also has the reputation as "the gift that keeps on killing" in that roaches that cross over lightly dusted areas do not die immediately, but that the effect is like shards of glass cutting them apart. This often allows a roach to go back 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.

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 is known to collect and sit. It is available in a gel form and injectable paste form for treating rot affected wood without the need to replace the timber. Concentrates of borate-based treatments can be used to prevent slime, mycelium, and algae growth, even in marine environments.
  • Boric acid is added to salt in the curing of cattle hides, calfskins, and sheepskins. This helps to control bacterial development, and helps to control insects.

pH buffer

Distribution between boric acid and borate ion versus pH assuming pKa = 9.0 (e.g. salt-water swimming pool)
 
Boric acid predominates in solution below pH 9
Buffer capacity of the boric acid - borate system versus pH assuming pKa = 9.0 (e.g. salt-water swimming pool)
 
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 pKa (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 pKa 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 salt-water 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 pKa1 = 6.0 and pKa2 = 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, but 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.

Lubrication

  • Colloidal suspensions of nanoparticles of boric acid dissolved in petroleum or vegetable oil can form a remarkable lubricant on ceramic or metal surfaces with a coefficient of sliding friction that decreases with increasing pressure to a value ranging from 0.10 to 0.02. Self-lubricating H3BO3 films result from a spontaneous chemical reaction between water molecules and B2O3 coatings in a humid environment. In bulk-scale, an inverse relationship exists between friction coefficient and Hertzian contact pressure induced by applied load.
  • Boric acid is used to lubricate carrom and novuss boards, allowing for faster play.

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. 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. BWRs use an aqueous solution of boric acid and borax or Sodium Pentaborate for an emergency shut down system. 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.

Pyrotechnics

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

Agriculture

  • Boric acid is used to treat or prevent boron deficiencies in plants. It is also used in preservation of grains such as rice and wheat.