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Unveiling the Mystery of Schiff Reagent: Composition Preparation and Test

Schiff Reagent: Its Composition, Preparation and TestSchiff’s reagent is a commonly used reagent in organic chemistry for the detection of aldehydes. The reagent is well-known for its characteristic color, which is magenta, and has been in use for over a century.

Developed by Hugo Schiff in 1866, Schiff’s reagent is a powerful tool in the identification of aldehydes and other compounds. This article delves into Schiff Reagent, its composition, preparation, and test.

Composition of Schiff Reagent

Schiff’s reagent is a complex mixture comprised of two main components: fuchsine and sodium bisulfite. Fuchsine, also known as basic fuschin or rosaniline hydrochloride is composed of three xanthene dye molecules and a triphenylmethane moiety.

Sodium bisulfite on the other hand is a white crystalline powder which is the sodium salt of bisulfite. Its formula is NaHSO3.

The combination of both reagents leads to the formation of Schiff’s reagent.

Preparation of Schiff Reagent

The preparation of Schiffs reagent is not a complex process. A typical recipe for making 100 ml of Schiff’s reagent is as follows:

– Dissolve 0.5 g of basic fuchsin in 100 ml of boiling water.

– Add 5 ml of concentrated hydrochloric acid (HCl) to the mixture. – Add 5g of sodium bisulfite (Na2S2O5) to the mixture, and stir until it dissolves.

– Heat the mixture to nearly boiling, and then immediately remove from heat. – Allow it to cool and add 1.5g of activated charcoal to the mixture.

– Leave the mixture to stand for about 30 minutes and then filter it. The product obtained is Schiff’s reagent.

It is essential to note that this preparation process was only for a 100 ml Schiff’s reagent solution, and the proportions are adjustable according to the desired concentration of the reagent.

Schiff Reagent Test

Schiffs reagent test is a powerful means of identifying aldehydes since it forms colored compounds with them. It is also used in other tests such as the Ehrlich’s reagent test, which is used to detect different indole derivatives including tryptophan and serotonin.

When Schiff’s reagent comes into contact with an aldehyde, it forms a stable hydrazone that gives a bright magenta color. The reaction can be carried out by either adding Schiff’s reagent directly to the sample or vaporizing the Schiff’s reagent above the sample.

Glucose and Schiff Test

Non-aldehyde reducing sugars such as glucose, fructose, and sucrose cannot undergo Schiff’s test. This is because the open structure of the sugars can isomerize into cyclic acetals, which are more stable and do not react with Schiff’s reagent.

In a systematic reaction, Schiff’s reagent reacts with the carbonyl group in aldehydes or ketones to form an imine, which is essentially a hydrazone of the aldehyde or ketone. The imine is often the basis for the formation of other compounds.


In summary, Schiff’s reagent has been an invaluable tool in organic chemistry since its discovery by German chemist Hugo Schiff in the 19th century. Its composition is mainly fuchsine and sodium bisulfite, and its preparation is straightforward, making it a popular reagent in the identification of aldehydes.

The test involves the formation of hydrazones that give the reagent its characteristic magenta color. While Schiff’s test is primarily used for aldehydes, it is not feasible for non-aldehyde reducing sugars such as glucose.

In summary, Schiff’s reagent is an essential tool in organic chemistry for the identification of aldehydes. Its composition is fuchsine and sodium bisulfite, and its preparation is simple.

The test involves the formation of hydrazones, which gives the reagent its characteristic magenta color. While Schiff’s test is not feasible for non-aldehyde reducing sugars, it remains a valuable asset in the field of chemistry.

The takeaway is that Schiff’s reagent is crucial in identifying key chemical compounds and plays a critical role in scientific research.

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