Definition: What is Schiff Reagent?

Schiff reagent is the product formed in some dye formulation reactions, such as the reaction between sodium bisulfite and fuchsine. It is used to check for the presence of aldehyde in an analyte. It can be used to differentiate between aldehydes and ketones. Fuschsine or rosaniline hydrochloride is a magenta-colored dye with a chemical formula C₂₀H₂₀N₃·HCl, which is decolorized by sodium bisulfate ^[1,2].

Composition of Schiff Reagent ^[3]

Schiff reagent has a chemical formula given by C₁₉H₂₁N₃S₂O₇·4H₂O and is composed of:

Basic Fuchsin Hydrochloride (C₂₀H₁₉N₃·HCl): <1%

Hydrochloric Acid (HCl): <1%

Sodium Metabisulfite (Na₂S₂O₅): <1%

Water (H₂O): >98%

Preparation of Schiff Reagent ^[4]

1. Dissolve 5 g of basic fuchsine in 900 ml of boiling distilled water
2. Cool to approximately 50 °C and slowly add 100 ml of 1M HCl
3. Cool to approximately 25 °C and dissolve 10 g of Na₂S₂O₅
4. Shake for 3 minutes and incubate in the dark at room temperature for 24 hours
5. Add 5 g of fine activated charcoal and shake for 3 minutes
6. Filter solution (should be clear)
7. Store at 4 °C in a foil-covered bottle

Schiff Reagent Test

When an unknown solution containing aldehyde is added to the colorless Schiff reagent, it reverts to its original magenta color. This test is known as the Schiff test ^[5,6].

The history of the Schiff test goes back to 1866 when German-Italian chemist Hugo Schiff developed it and reported it in a journal.

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