Boric Acid (H3BO3)
Metals & Non-Metals > Boron Family
 Chemical structure of  Boric acid Chemical structure of Boric acid

Boric acid, also known as boracic acid or orthoboric acid, is naturally occurring compound of Boron. It occurs in minerals borax, boracite, boron atrocaicite and colemanite. It is also found in seawater, plants and in fruits.

 White crystalline orthoboric acid powder White crystalline orthoboric acid powder

Orthoboric acid, H3BO3 is a white crystalline solid, with soapy touch. It is sparingly soluble in water but highly soluble in hot water.

Preparation methods:
It can be prepared by acidifyng an aqueous solution of borax.

It is also formed by the hydrolysis (reaction with water or dilute acid) of boron compounds (halides, hydrides, etc.).

BX3 + 3 H2O → B(OH)3 + 3 HX (X = Cl, Br, I)
B2H6 + 6 H2O → 2 B(OH)3 + 6 H2
hydrogen-bonding The dotted lines represents the hydrogen-bonding

Boric acid has a layer structure in which planar BO3 units are joined by hydrogen bonds.

Boric acid is a weak monobasic acid. It is not a protonic acid but acts as a Lewis acid by accepting electrons from a hydroxyl ion.

On heating, orthoboric acid above 370K forms meta boric acid, HBO2 which on further heating yields boric oxide, B2O3

Boric acid solution Boric acid solution used as an eye wash Eye problems like dryness, redness, watering eyes, and burning or itching sensation can be treated with the use of boric acid eye wash

Uses of Boric acid :

  • As an insecticide and fungicide.
  • As a mild antiseptic. Boric acid solutions used as an eye wash.
  • As a neutron absorber in nuclear power plants, to slow down the rate of fission reaction.
  • As a lubricant on ceramic or metal surfaces.
  • As a flame retardant.