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Home > Articles > Fehling Test: Definitions, Objectives, Solution, Principles, Process, Requirements, Result, Uses, and Limitations
Updated on 01st July, 2023 , 5 min read
One of the most commonly used tests for estimating or identifying reducing and non-reducing sugars is the Fehling test. It is frequently used to discriminate between functional groups of ketones and water-soluble carbohydrates using this test developed by the German scientist H.C. Von Fehling.
The Fehling test is a prominent method for estimating or detecting reducing and non-reducing sugars. The test devised by H.C. Von Fehling, a German chemist, is also used to distinguish between ketone functional groups and water-soluble carbohydrates.
Detecting reducing sugars and differentiating between water-soluble carbohydrates and ketone functional groups is done using the Fehling test. To distinguish between reducing and non-reducing substances, a deep blue alkaline solution is employed to identify the presence of aldehyde or any groups containing the aldehyde functional group -CHO in addition to Tollen's reagent. To discriminate between a ketone group and water-soluble carbohydrates, use the Fehling solution. The test was created in 1849 by German chemist Hermann von Fehling. A Fehling solution is used in the test to ascertain the result. The preparation of the Fehling solution, the Fehling test method, and associated reactions. The Fehling test is carried out by heating the test material while using the Fehling solution. Brick-red precipitate development indicates the presence of an aldehyde group.
The Fehling test has numerous goals, but two of its most popular applications are as follows-
The Fehling Solution is created by combining two different solutions. The first is Rochelle salt, produced strongly with sodium hydroxide, which is a colorless solution and is known as Fehling A solution. The second is copper sulfate, which is a deep blue aqueous solution and is known as Fehling B solution. The Fehling Solution is created by combining the Rochelle salt and copper sulfate from the A and B solutions. Additionally, each of the solutions—A and B—is produced independently and kept during the assessment. The active chemical in this reaction is the tartrate complex, which acts as an oxidizing agent.
The following are some of the principles of the Fehling test-
The following are some of the steps to do the Fehling test-
Precaution: Fehling solution frequently has a caustic character. Wearing protective clothing, such as gloves and goggles, is therefore always preferable.
The following are some of the requirements of the Fehling Test-
The following are the results of the Fehling test-
The Fehling tests have several applications, some of which are listed below-
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By - Nikita Parmar 2024-09-06 10:59:22 , 6 min readAns. The test was created in 1849 by German chemist Hermann von Fehling (9). The quantity of reducing sugars may be determined, and the glucose equivalent of starch sugars may be calculated using the Fehling reagent.
Ans. Fehling solutions A and B are maintained apart since mixing them will cause the bistartratocuprate (II) complex to rapidly deteriorate.
Ans. A successful outcome is indicated by the production of a brick-red copper (I) oxide precipitate upon boiling. Methane creates copper metal as a result of its potent reducing ability; ketones do not.
Ans. No, the Fehling test cannot be used for aromatic alcohol.
Ans. Sucrose does not diminish Fehling’s solution because it does not contain a free aldehyde or ketone group.
Ans. Yes. The Fehling test may be applied to formaldehyde.
Ans. Any aldehydic chemical containing alpha hydrogen will result in a positive Fehling test. Alpha hydrogen is present in both formaldehyde and acetaldehyde. Both compounds will thus pass the Fehling test.