Glucose gives red colour in Fehling’s test.
- Fehling’s reagent, a blue-colored basic bistartratocuprate(II) complex solution, is mixed with three different aqueous sugar solutions in warm water beakers.
- In the presence of glucose and fructose, a brick-red precipitate develops.
- In the test tube containing sucrose solution, there is no response.
Uses of Fehling’s Test
- It is used to determine whether a carbonyl group is an aldehyde or a ketone. Aldehydes tend to get oxidized and give a positive result. Ketones apart from alpha-hydroxy-ketones do not react.
- Fehling’s test is also used as a general test for monosaccharides where a positive result is obtained for aldose monosaccharides and ketose monosaccharides.
- It is also used in the medical field to determine the presence of glucose in urine. It helps to know whether the person is diabetic or not.