Fehling's test & Biuret test

Fehling's test & Biuret test
The practical in chemistry lab are done with the help of reagents. Without reagents experiments are not possible. Here is an article which is related to the important tests in chemistry.

Fehling's test
Actually what is fehling's test? This is a test that is related to reducing sugars & aldehydes. You might be thinking about the reagent that is used in fehling's test. It is fehling's solution.

Fehling's solution
Fehling's solution consists of fehling's A & fehling's B solutions. Fehling's A is copper sulphate solution & fehling's B is alkaline sodium potassium tartrate solution. Sodium potassium tartrate is also known as Rochelle salt.Students should know both the names.

How is the fehling's test done?
Fehling's A & Fehiling's B are mixed in equal volumes. To one ml of the reagent taken in a test tube a little organic substance is added & boiled on a water bath. In the result a brick red precipitate is formed. This indicates the presence of reducing sugars & aldehydes.

Biuret test
Every student has the opportunity to do this test in the lab when they are given urea for analysis. The details of urea are discussed in another article in this section itself. For doing this test, 2 reagents are used. They are NaOH solution & 1 % copper sulphate solution. So the biuret reagent consists of NaOH solution & 1% copper sulphate solution.

What is the procedure for biuret test?
Biuret test is actually a confirmatory test for urea. For this you have to take a boiling tube. In this a little of the given substance is added & heated until it melts & then solidifies. Cool for a while & dissolve the residue in little water .Add dilute solution of copper sulphate followed by sodium hydroxide solution drop by drop to the test tube. Observe what happens? You can notice the presence of violet color in the test tube. So the appearance of a violet color indicates the presence of urea in the given substance.

The important point is that if a student finds the experiment interesting then each & every change in the experiment will be observed with a good attitude.