Reagent

Substance added to a system to cause a chemical reaction

In chemistry, a reagent ( ree-AY-jənt) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. A reactant is a substance or compound that is consumed in a chemical reaction. The terms reactant and reagent are often used interchangeably, but reactant specifies a substance consumed in the course of a chemical reaction; reagent is used in the context of chemical analysis, while reactant is used in the context of reaction itself.

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