Neutralization

Neutralization is a process in which the effect of a substance is countered or made ineffective by another substance, typically forming a stable, non-harmful product. The term is used across disciplines with related ideas of cancellation, balancing, or inactivation.

In chemistry, acid–base neutralization refers to reactions between acids and bases that produce a salt and water. In aqueous solution, hydrogen ions from the acid react with hydroxide ions from the base to form water, while the remaining ions form a salt. The reaction is usually exothermic. In titration, the equivalence point marks when the reacting amounts are stoichiometrically equal. Indicators signal this point. Reactions can differ with strong or weak acids/bases, and buffers may influence the approach to neutrality.

In biology and medicine, neutralization describes the ability of antibodies or other factors to block the biological activity of a pathogen or toxin. By binding to a critical site on a virus, bacterium, or toxin, neutralization can prevent infection or enzymatic action. Neutralization assays quantify this effect, often by measuring decreases in infectivity or activity in cell-based readouts.

In environmental engineering and industry, neutralization refers to adjusting pH or reacting hazardous substances with counteragents to reduce reactivity or toxicity. Examples include lime treatment of acidic wastewater or mine drainage to raise pH and precipitate metals, and neutralizing spilled acids to protect ecosystems and workers.

The concept also appears in other contexts as a general means of counteracting or inactivating an undesirable factor. The specifics of neutralization depend on the substances involved, the medium, and the intended outcome.