What is Boric Acid (H3BO3)?

h3bo3Boric Acid is a monobasic Lewis acid with the chemical formula H3BO3.

It is an acid-containing compounds of boron, oxygen, and hydrogen. Boric acid is also known as acidum boricum, hydrogen borate, boracic acid, and orthoboric acid. It is a weak acid and has antiviral, antifungal, and antiseptic properties.
Boric acid is soluble in water and does not have any characteristic odour. Under standard conditions, this compound exists either as a colourless crystal or in a white powdery form. Boric acid can be prepared by reacting borax with hydrochloric acid. It can be noted that Wilhelm Homberg was the first person to prepare boric acid from borax.

Boric Acid as a Medicine
Boric acid is widely used as an antiseptic for the treatment of minor cuts and burns. Furthermore, this compound is also used in medical dressings and salves. Very dilute solutions of boric acid can be used as an eyewash. Owing to its antibacterial properties, boric acid can also be used for the treatment of acne in humans. In its powdered form, it can also be sprinkled into socks and shoes to prevent the athlete’s foot (tinea pedis).
It is important to note that boric acid can prove poisonous if consumed or inhaled in relatively large quantities. Furthermore, continued exposure to boric acid over long durations of time can severely damage the kidney.

Properties of Boric Acid – H3BO3
Under standard conditions for temperature and pressure (STP), boric acid exists as a white, crystalline solid that is fairly soluble in water. The solubility of H3BO3 in water is temperature-dependent. At a temperature of 25 °C, the solubility of boric acid in water is 57 g/L. However, when the water is heated to 100 °C, the solubility of this compound increases to approximately 275 g/L. It can also be noted that boric acid is sparingly soluble in pyridine and slightly soluble in acetone. The conjugate base of boric acid is the borate anion.
The acidity of solutions of boric acid is known to increase with polyols containing cis-vicinal diols (like mannitol and glycerol). The value of pK of B(OH)3 is known to extend to five orders of magnitude (from 9 to 4), under different concentrations of mannitol. It can be noted that in the presence of mannitol, the solution of boric acid with increased acidity can be referred to as mannitoboric acid.

Structure of H3BO3 Molecules
Each boric acid molecule features boron-oxygen single bonds. The boron atom occupies the central position and is linked to three hydroxide groups. The overall molecular geometry of boric acid is trigonal planar. The structure of H3BO3 molecules is illustrated below.

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