Color reaction

In chemistry, a color reaction is a chemical reaction that is used to transform colorless chemical compounds into colored derivatives which can be detected visually with the aid of a color reagent.

The concentration of a colorless solution cannot normally be determined with a colorimeter. The addition of a color reagent leads to a color reaction and the absorbance of the colored product can then be measured with a colorimeter.

Many different color reagents have been developed for determining the concentrations of different substances. For example, Nessler's reagent can be used used to determine the concentration of a solution of ammonia.

In thin layer chromatography (TLC) color reactions are frequently used to detect compound spots by dipping the plate into the reagent or by spraying the reagent onto the plates.