Schiff's reagent is a chemical preparation used to test a solution for the presence of aldehydes. It is composed of rosaniline and sulfurous acid dissolved in water. When the reagent is added to a solution that contains aldehydes, it turns bright pink in color.
Schiff's reagent is named after Hugo Schiff, a German chemist who lived from 1834 until 1915, and who first used this preparation to test for the presence of aldehydes when performing organic chemistry reactions. The process of adding the reagent to a chemical solution is referred to as Schiff's test. It is one of the earliest organic chemistry dye tests to have been widely used for detection of a certain functional group in chemical solutions.
Schiff's reagent is also sometimes used to dye organic tissues. When used for this purpose, several drops of the reagent are added to a slide containing human or animal cells. Those which contain aldehyde groups react with the reagent to give off a pink color, which makes it easier to observe detail under a light microscope. In most procedures, Schiff's reagent is used along with one or more other stains that react with different functional groups to create slides in which different cells take on different colors. This makes it easier to differentiate between various cell and tissue types.