Measure of the capacity of aqueous media to react with hydrogen ions.
Notes: - Alkalinity is used to assess the buffering capacity of natural waters and is measured by titration using methyl red (pH 4.5, total alkalinity) or phenolphthalein (pH 8.3, composite alkalinity).
- Alkalinity is often expressed as an equivalent mass concentration of calcium carbonate, for example "alkalinity equals \(\pu{3.2 mg L-1}\) as \(\ce{CaCO3}\)."
Source:
PAC, 2025, 97, 137. 'Glossary of terms for mass and volume in analytical chemistry (IUPAC Recommendations 2024)' on page 2 (https://doi.org/10.1515/pac-2023-0903)