Overview

Titration is a common laboratory method of quantitative chemical analysis used to determine the concentration of an unknown solution by reacting it with a reagent of known concentration. Often called volumetric analysis, a titration finds the amount of analyte by measuring the precise volume of titrant required to complete a stoichiometric reaction. The technique underpins many routine checks in industry, environmental testing, medicine and research and is introduced in basic chemistry courses as a foundational analytical tool. For a general description see quantitative chemical analysis.

Basic principle and calculation

In a titration a measured volume of the solution of unknown concentration (the analyte or titrand) is mixed with an indicator or probe and titrated by carefully adding a solution of known concentration (the titrant). The titrant is delivered from a burette until the reaction reaches the equivalence point, where stoichiometrically equivalent amounts of reactants have combined. The number of moles of titrant added equals the number of moles of analyte consumed according to the balanced chemical equation. In practical terms one uses the relation n = M × V (moles = molarity × volume) and the stoichiometric coefficients from the reaction to calculate the unknown molarity. For examples of unknown concentration calculations see unknown concentration.

Equipment, indicators and aids

  • Volumetric glassware: a pipette for delivering a known aliquot of analyte and a burette for dispensing titrant are standard; these are sometimes described in equipment guides such as pipette and burette references.
  • Indicators: external color indicators (for example phenolphthalein or methyl orange) change color near an endpoint; internal indicators such as potassium permanganate act as both reagent and visual marker in some redox titrations — see potassium permanganate.
  • Standards and titrants: titrants must be prepared from reliable primary standards or standardized by titration themselves; guidance on preparing and standardizing titrants is available through sources on reagents and titrants.

Types of titration and examples

There are several common classes of titration, each exploiting different reaction types. Acid–base titrations determine acidity or alkalinity by neutralization (e.g., HCl vs NaOH with phenolphthalein). Redox titrations rely on electron transfer; a classic example is titration with standardized KMnO4 to quantify Fe2+. Complexometric titrations use chelating agents like EDTA to measure metal ions and are widely used to determine water hardness. Precipitation titrations and nonaqueous titrations address analytes that are insoluble or react slowly in water.

Endpoint versus equivalence point; modern detection

It is important to distinguish the equivalence point (the exact stoichiometric completion) from the endpoint (the observed change such as a color shift). Proper selection of an indicator ensures the endpoint closely matches the equivalence point. Instrumental detection improves accuracy: potentiometric titration measures potential differences with an electrode and a potentiometer to detect sharp changes in voltage near equivalence; see general information about potentiometry and electrodes. Other instrumental methods include conductometric, spectrophotometric and amperometric detection.

Procedure, sources of error and best practices

Typical steps include: delivery of a measured aliquot of analyte into a flask, addition of indicator if needed, slow addition of titrant from the burette with thorough mixing and observation for the endpoint, and recording the volume used. Common error sources are parallax when reading the burette, incomplete reactions, impurities in reagents, temperature effects and improper indicator choice. Volumetric precision and repeat titrations (concordant results) improve confidence in the calculated values. For a practical discussion about volumes and techniques consult references on volume measurement.

Applications and significance: Titration remains indispensable for quality control in pharmaceuticals and food, environmental monitoring (acid and base content, oxidants, metal ions), clinical laboratories and education. While automation and electronic endpoint detection have modernized many workflows, the conceptual simplicity and reliability of titration make it a lasting and widely taught analytical method.