neutralisant

Neutralisant, in chemistry, designates a substance that neutralizes the effects of acids or bases. It is commonly described as a neutralizing agent, capable of bringing the pH of a solution toward neutrality through an acid–base reaction. In general, acids react with bases to form a salt and water, and the choice of neutralisant depends on whether an acidic or basic medium must be corrected.

Common neutralisants include bases such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide, which neutralize acids; and carbonates or hydroxides used to neutralize bases in various contexts. Sodium bicarbonate and lime (calcium oxide or calcium hydroxide) are frequently employed to raise or stabilize pH in environmental, agricultural, and industrial settings. In soil management, lime is used to reduce soil acidity, improving nutrient availability for plants. In wastewater treatment and chemical processing, neutralising agents adjust pH to safe or required levels before discharge or further processing.

The neutralization reaction typically forms a salt and water, though the exact products depend on the reactants. For example, sodium hydroxide reacting with hydrochloric acid yields sodium chloride and water. The choice of neutralisant is guided by factors such as desired final pH, buffering capacity, temperature effects, and safety considerations, since some neutralisation reactions are exothermic and can release heat or gases.

Neutralisant is also used in consumer products and clinical settings, where controlled neutralization helps relieve acidity, stabilize formulations, or mitigate corrosive effects.