Molisch test is a qualitative test for determining the presence of carbohydrates in a solution.It is named after an Austian botanist “Hans Molisch” who discovered this test for the presence of carbohydrates.
It is a general test for the presence of carbohydrates and is positive for all kinds of carbohydrates which in free from or in combined form.
Principle of molish’s test:-
For detecting the presence of carbohydrates, the solution is first treated with a strong acid.This is for hydrolysing the carbohydrate to monosacharide.When water is removed from monosaccharides, a compound called furfurol is formed.This furfurol is condensed to form a violet ring or other colored compound.The compound furfurol is condensed with alpha nephthol or other phenol present in molisch’s reagent.
Importance of molisch’s test:-
Molisch test is very important because it is a general test for the presence of carbohydrates.It is used widely as compared to other tests because before every specific test for different carbohydrates a general test is important and that general test is performed via molisch test.Another important thing is that, this test is positive for all types of carbohydrates whether free or in combined form like glycoprotiens,glycolipids etc.
Procedure of Molisch’s test:-
If you want to find the presence of carbohydrates in a given solution then just follow the below procedure of molisch test and you will find whether the given solution contains carbohydrates or not.
- Take 5ml of solution in a test tube with the help of pipette.
- Add two to three drops of molisch reagent.
- Mix it gently for some time.
- Incline the test tube and slowly add a few drops of strong mineral acid.(Sulphuric acid or hydrochloric acid).
- You will observe reddish violet ring formed at the junction of the acid and carbohydrate solution.
Precautions of Molisch test:
Here are some of the things you would need to take care of while performing this test:
- First of all the most important thing you need to know is to add acid at the side of test tube. Don’t add it directly.
- Then you would need to add acid drop by drop. Do not add all the acid once.
- Measure the solution before adding it.
- Add only few drops of molisch’s reagent. You don’t need to add much.
- Add acid with great care as we use strong acid in this test and it could burn your skin.
- Don’t shake the test tube when ring is formed. If you do so, you would destroy the ring.
If you perform all the steps as mentioned above correctly, you would definitely get a positive result, i.e violet ring if carbohydrates are present in your solution.