Molischs Test, Principle and other Facts
October 2, 2016 by Admin Leave a Comment
In the vast field of science, there are many tests that are used to check the
presence of carbohydrates but the simplest, easiest and most successful of
them is Molischs test. Here in this article, youre going to learn things such as
1. What is the Molisch test? 2. The principle of Molischs Test. 3. Molisch
Reagent and 4. Procedure and Precautions for this test. I tried my best to
write this in simplest of words so that people even with weak English can
understand it better and have a better grasp over their study.
What is Molischs Test?
Molish test is a delicate synthetic test for the checking of present
carbohydrates, in light of the lack of hydration of the sugar by sulfuric acid or
hydrochloric acid to deliver an aldehyde, which consolidates with two particles
of phenol bringing about a red-or purple-hued compound. This test was
named after a Botanist from Austria Hans Molisch. This test is considered as a
very easy to understand test for a student of all levels and thats why it is the
most used. Molischs test works on a simple principle which is explained
elaborately in the next heading.
Principle of Molischs Test:
To detect the presence of carbohydrates, the solution is first treated with a
strong acid.This is for hydrolyzing the carbohydrate to monosaccharide. A
compound named furfurol is then made when water is removed from
monosaccharides. This furfurol is consolidated to shape a violet ring or other
shaded compound.The compound furfurol is dense with alpha-naphthol or
other phenol present in molischs reagent.
Molischs Reagent:
In every chemical test, it is necessary that you must prepare a reagent.
Reagent much is compatible and right according to the needs of the test. Here
to perform Molischs Test our reagent will be a-naphthol which is dissolved in
ethanol and this is used in the test tube. This is the best reagent that could be
prepared for the test and is completely compatible with the test. Once
prepared this can be further used in the procedure of checking the presence
of Carbohydrates in a solution with the help of Molischs test.
Procedure involved in Molischs Test:
To do Molischs test there is not very complex procedure involved. In fact, you
can do it easily if you have basic chemistry knowledge and also basic
knowledge of all the equipment involved in the procedure. Just follow this
simple guide and you can easily find the presence of carbohydrates with the
help of Molischs test.
1. First, you will need to gather some equipment involved in the process.
First thing is to take a good test tube and a pipette. Once you have these
two, you can continue with the procedure.
2. Now in the test tube, insert 5 ml solution. Make sure that you do this
with the help of pipette and IU have already told you to arrange it. If you
put it directly, you might do some mistake in the quantity of the solution.
3. Take the reagent which you using and two or three drops of it in the
solution. Dont exceed the amount from two to three drops because it
might affect the test and you wont get good results.
4. Once if you have added the drops of reagent, mix it gently by shaking or
moving the test tube around. Do the mixing for quite some time till it gets
mixed completely.
5. Now you will need to add little drops of any of the strong minerals acids
such as hydrochloric acid or Sulphuric acid. Make sure that when you
add these, make sure that you hold the test tube inclined. Now you are
done with the test but what was the result?
6. You will know the results are positive or there are carbohydrates present
in the by the formation of the violet reddish ring formed at the
carbohydrate and acid meeting point.
Note: Dont perform the test before you have taken care of few very important
things. But what are those thing? That is what youre going to know in the next
heading.
Precaution before performing Molischs test:
Here is a list of some very important precautions that you need to take before
and while performing the Molischs test.
1. This is the most important precaution because the whole test depends
on it. Always make sure that you have measured the solution before
using it in the test because the quantity of this solution is everything and
it directly effects the results of the test.
2. 2nd this is also a very important one. When you add the acid that you
have chosen for the solution, make sure that it is not being added
directly. Means that you add the acid in the test tube from the sideways
or you can say by dropping it down the wall of the test tube. This wont
cause the acid to react quickly and your whole procedure will remain
smooth and simple.
3. Do not pour down all the acid at once. Make sure that you add the acid
slowly and in drop by drop order. Pouring it down could cause the
sudden reaction and your whole procedure could be lost.
4. Few drops of Molisch reagent are enough to serve the purpose. Adding
too much is not a very good idea since a reagent could prove harmful
when added in more quantity.
5. Never ever shake the reddish violet ring once it is formed. Shaking the
ring destroys all your work and you will have to go through the whole
procedure again.
6. The acid that is being used in this procedure is a strong acid and is very
dangerous for skin. So when you are adding the acid, pour it gently.
Wearing skin protective gloves are also very crucial but if you dont have
them, you can rely on pouring the acid gently.
Result of Molisch Test:
Once youve followed the whole procedure carefully along with taken
precautions there are almost 100% chances that your result will be positive. It
should be a reddish violet ring formed at the point where acid and
carbohydrates are meeting.
Molischs test-Qualitative test for the presence of carbohydrates
August 6, 2016 by Admin 54 Comments
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.
<photo credit>
Principle of molishs 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 molischs reagent.
Importance of molischs 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 Molischs 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.
1. Take 5ml of solution in a test tube with the help of pipette.
2. Add two to three drops of molisch reagent.
3. Mix it gently for some time.
4. Incline the test tube and slowly add a few drops of strong mineral acid.(Sulphuric acid or
hydrochloric acid).
Observation
5. 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. Dont 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 molischs reagent. You dont need to add much.
Add acid with great care as we use strong acid in this test and it could burn your skin.
Dont shake the test tube when ring is formed. If you do so, you would destroy the ring.
