The difference between the highest and lowest members of a series. This term is not recommended.
Source:
Orange Book, 2nd ed., p. 5 (https://media.iupac.org/publications/analytical_compendium/)
See also:
PAC, 1994, 66, 595. 'Nomenclature for the presentation of results of chemical analysis (IUPAC Recommendations 1994)' on page 599 (https://doi.org/10.1351/pac199466030595)