Older unit

Normalityis an older unit of concentration that, although once commonly used, isfrequently ignored in today’s laboratories. Normality is still used in some hand-books of analytical methods, and, for this reason, it is helpful to understand itsmeaning. For example, normality is the concentration unit used in Standard Meth-ods for the Examination of Water and Wastewater,1a commonly used source of ana-lytical methods for environmental laboratories.Normalitymakes use of the chemical equivalent, which is the amount of onechemical species reacting stoichiometrically with another chemical species. Notethat this definition makes an equivalent, and thus normality, a function of thechemical reaction in which the species participates. Although a solution of H2SO4has a fixed molarity, its normality depends on how it reacts.