Reagents and laboratory chemicals include substances of sufficient purity for use in chemical analysis, chemical reactions or physical testing. Purity standards for reagents and laboratory chemicals are set by organizations such as ASTM International or the American Chemical Society.
More technically, IUPAC defines a reagent as a substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Reagents may be either organic or inorganic compounds that are commonly used for analytical purposes such as chemical analysis, physical testing or testing of chemical reactions.
Organic reagents include Collins reagent (for oxidizing primary alcohols), Fenton's reagent (to oxidize contaminants) and Grignard reagents (to form carbon-carbon bonds). Analytical reagents include Fehling's reagent and Tollen's reagent (both test chemical functionality) and Millon's reagent (to detect soluble proteins).