Acids, Bases and Salts

Boric Acid

Boric acid (Hydrogen Borate, boracic acid or acid boricum) is a weak acid by nature. Generally, it is useful as an antiseptic, insecticide, flame retardant, or neutron absorber. It is also useful as a precursor to other chemical compounds. Actually, borax and boric acid are the same thing and are associated with producing homemade laundry soap. Borax is being extracted from the tourmaline, kernite, and colemanite and then further it is refined. Mineral sassolite can be extracted from boric acid. Boric acid is popular as one of the most effective and natural way to get rid of those pesky pests at our home.

Boric Acid

                                                                                            Boric Acid

Introduction to Boric Acid

Its molecular formula is \(H_{3}BO_{3}\). It is also represented as \(BH_{3}O_{3} or H_{3}BO_{3} or B(OH)_{3}\). Boric acid is an acidic chemical compound. It is containing four atoms of oxygen, one atom of phosphorus, and three atoms of hydrogen. As per the strength, it is a weak acid but it is having antiviral, antifungal, and antiseptic properties. Boric acid is soluble in water easily, whereas it does not have any characteristic odour. With the standard conditions, it exists either as a colourless crystal or in the form of white powder.

It can be prepared by reacting borax with hydrochloric acid. Wilhelm Homberg was the first person, who has prepared boric acid from the borax in the laboratory. Boric acid is having its application widely as an antiseptic for the treatment of minor cuts and burns. Also, it is useful for the purpose of medical dressings and salves.

Very dilute solutions of the boric acid can be useful as eyewash. Due to its antibacterial properties, boric acid can is widely useful for the treatment of acne in humans. Not only this, in its powdered form, it can also be sprinkled into socks and shoes to prevent athlete’s foot. It must be noted that boric acid can prove poisonous if consumed or inhaled in a relatively large amount. Also, its continuous exposure over long durations of time can severely damage the kidney too.

Preparation of Oxalic Acid

In a simple way, one may prepare the boric acid by reacting borax with any mineral acid such as hydrochloric acid. Its chemical equation is:

\(Na_{2}B_{4}O_{7}.10H_{2}O + 2HCl \rightarrow 4H_{3}BO_{3} + 5H_{2}O + 2NaCl\)

We may also, prepare it from the hydrolysis of diborane and trihalides of boron (for example boron trichloride or boron trifluoride). It is the monobasic and a weak type of Lewis acid of the Boron element.


Physical Properties

  1. Under the STP, boric acid exists as a white, crystalline solid.
  2. It is fairly soluble in water. Its solubility in water is temperature-dependent.
  3. At the temperature of 25 degrees Celsius, its solubility in water is 57 grams per litre. But, when the water is heated to 100 degrees Celsius, its solubility increases up to approximately 275 grams per litre.
  4. It can also be noted that boric acid is sparingly soluble in pyridine whereas slightly soluble in acetone. The conjugate base compound of boric acid is the borate anion.
  5. Its boiling point is 158 degrees C and its melting point is 300 degrees C.
  6. Its density is 1.435 gram per cubic cm.
  7. The value of its pK extends to five orders of magnitude, under different concentrations of mannitol.
  8. Also, in the presence of mannitol, the solution of boric acid with the increased acidity can be referred to as mannitoboric acid.

Chemical Properties 

  1. Its molar mass is 61.83 gram per mole.
  2. Each boric acid molecule is featuring with boron-oxygen single bonds.
  3. The boron atom is occupying the central position and is linked to three hydroxide groups.
  4. The complete molecular geometry of boric acid is the trigonal planar.
  5. This chemical compound occurs naturally and also it exists in combination with other minerals like borax and boracite. In the mineral form, it can be visible as sassolite.
  6. It works as a cleaning agent, and it has its application as a cleanser, disinfectant and deodorizer.
  7. One teaspoon of boric acid dissolved in four cups of water will treat sore eyes, weird eye discharge, as well as eye irritation. Its anti-fungal qualities are useful to treat vaginal yeast infections or candidiasis.
  8. Boric acid easily reacts with alcohols and hence to produce borate esters, \(B(OR)_{3}\). Here, R is alkyl or aryl. A dehydrating agent like concentrated sulfuric acid is typically added:

\(B(OH)_{3} + 3 ROH \rightarrow B(OR)_{3} + 3 H_{2}O\).

Heating the boric acid, gives metaboric acid:

\(H_{3}BO_{3} \overset{170^{0}C}{\rightarrow} HBO_{2} + H_{2}O\)

Further, at 300 degrees  C, \(HBO_{2}\) gives tetraboric acid:

\(4HBO_{2} \overset{300^{0}C}{\rightarrow} H_{2}B_{4}O_{7} + H_{2}O\)

Uses of the Boric Acid

Some major uses of boric acid are as follows

  1. In the manufacture of textile fibreglass and in the production of the flat panel display
  2. To neutralize the active hydrofluoric acid
  3. For blacksmiths for welding flux and also in electroplating.
  4. In the jewellery industry and also for the manufacturing of silly putty
  5. An Insecticidal and as an antiseptic and antibacterial chemical.
  6. On the carrom boards as a dry lubricant.
  7. A neutron poison in some nuclear plants too.
  8. To preserve grains like wheat and rice.
  9. As the cross-linking and gelling agent in combination with guar gum. And hence, regulates the viscosity and rheology of the drilling fluid.

FAQs about Boric Acid

Q.1: How do we neutralize boric acid?

Answer: The acidic and fundamental properties of both the acid as well as base are damaged by neutralization. Lime and baking soda are two inexpensive chemicals that may neutralize acids and these are easily available.

Q.2: Can boric acid be soluble in acetone?

Answer: Boric acid is the crippling poison. It is partially soluble in acetone in water, glycerol, ether, methanol, as well as liquid ammonia. Boric acid can be derived from the borax, or by hydrolysing the halides or hydrides of the boron. But, crystals of boron oxide are a little bit soluble in cold water and more soluble in hot water.

Q.3: Boric acid is good for the skin or not?

Answer: There are some easily visible signs and symptoms due to brief exposure to boric acid. Boric acid is having low toxicity if eaten or if it contacts the skin. But, in the form of borax, it becomes corrosive to the eye as well it is very irritating to the skin.

Q.4: Mention the side effects of boric acid suppositories.

Answer: Side effects due to boric acid suppositories, which one should report to the doctor immediately are allergic reactions like skin rash, itching, vaginal irritation, redness, or burning.

Q.5: Mention some Health hazards of Boric Acid.

Answer: Boric acid is a kind of dangerous poison. Chronic poisoning may occur in those who are repeatedly exposed to boric acid. Such people who have regular exposure to it may get sick, and even may die also.

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