Reagent

A reagent is a substance or compound added to a system to cause a chemical reaction or to test for a specific property. In many contexts, reagents are substances that participate in a reaction, either as reactants that are consumed, or as catalysts that facilitate the process without being consumed in the overall transformation. The term is often contrasted with solvents, which provide the medium for a reaction, and with purely inert materials that do not participate in the chemistry. Reagents can be broadly categorized by their function, such as oxidizing agents, reducing agents, acids, bases, dehydrating agents, complexing ligands, or indicators used in analytical procedures.

In chemistry, common reagents include acids like hydrochloric or sulfuric acid, bases such as sodium hydroxide, oxidants like potassium permanganate, and reducing agents such as sodium borohydride. Reagents also encompass specialized reagents used in organic synthesis, including coupling reagents, dehydrating agents, and protective-group reagents. In analytical chemistry, reagents are selected for their ability to produce a measurable change (color, precipitate, or fluorescence) in the presence of a target substance, as seen with Benedict’s reagent or silver nitrate for halides.

In biology and biochemistry, reagents include buffers, enzymes, antibodies, dyes, nucleic acid probes, and various staining or assay components. In materials science and industrial chemistry, reagents serve as precursors or catalysts in the preparation of polymers, ceramics, and other materials.

Purity and labeling are important aspects of reagents. Reagent grade or analytical reagent (AR) designation signals a high level of purity appropriate for laboratory use. Safety data sheets, proper storage conditions, and strict handling procedures are standard obligations for acquiring and using reagents.