Fehling,s test

To test the presence of carbohydrates in the given solution

1. Aim :- To Test the presence of carbohydrates in the given sample using Fehling’s Test Lecture by:- Dr. Mohan Kumar Assistant professor Gyan Joyti Collage of Pharmacy, Hazaribag Email:- [email protected]

2. Experiment:-2 Aim :- To Test the presence of carbohydrates in the given sample using Fehling’s Test Theory: This test is given by reducing sugars. To the aqueous solution of carbohydrate fehling’s solution is added and heated in water bath. Formation of red precipitate confirms the presence of reducing sugars. The copper ions present in fehling’s solution in +3 state is reduced to +2 oxidation state and in alkaline medium it is precipitated as red cuprous oxide.

3. Materials required: Fehling’s reagent Glucose solution Test tubes Measuring cylinder Pipette Test tube holder Test tube stand Bunsen burner Water bath Dropper Stirrer Distilled water

4. Procedure: Fehling’s solution A can be prepared by  dissolving copper sulfate in distilled water and add a few drops of sulfuric acid. Fehling’s solution B can be prepared by  dissolving sodium potassium tartrate and sodium hydroxide in 150ml of distilled water. Fehling’s reagent be prepared by making a solution of 1ml each Fehling’s A and Fehling’s B. Take 2ml of given sample solution in a clean test tube. Add 2 ml of Fehling’s solution A and Fehling’s solution B to it. Keep the solution in a boiling water bath for about 10 minutes. If there is formation of red precipitate then the presence of carbohydrate is confirmed.

5. Take sample of sugar solution Heat the Mixture of fehling’s reagent and sample sugar Mixture of fehling’s reagent and sample sugar Take fehling’s reagent

6. Observations: Test Glucose Lactose Sucrose Starch Fehling’s test Red precipitate Red precipitate No precipitate No precipitate

7. Results and Discussions: The given organic compound is a reducing sugar. Precautions: Always use droppers to take reagents from the reagent bottles. While heating the reaction mixture do it carefully.