The document describes the Molisch test, which is used to test for the presence of carbohydrates. The test involves adding a sample solution to test tubes, then adding Molisch reagent and concentrated sulfuric acid. A positive result is indicated by a violet ring forming at the interface of the reagents. The test was performed on glucose, sucrose, starch, lactose, fructose, and ribose. Starch, lactose, fructose and ribose all tested positive by producing a violet ring. Glucose and sucrose did not produce rings, possibly due to excess acid or moisture interfering with the reaction. The Molisch test is a general test that can identify any carbohydrate.

1. Activity 3
Qualitative Tests for Carbohydrates
MOLISCH TEST
GENERAL TEST FOR CARBOHYDRATES
GROUP 5
BAYSA I BENITEZ I CARBAJAL I
GONZALES I SOLANIA

2. MOLISCH TEST
● Test for all carbohydrates
● Caries the name of Austrian Botanist
Hans Molisch (Vedantu, n.d)
● Effective for identify any substance
that, in the presence of H2SO4, can
dehydrate to furfural or
hydroxymethylfurfural

3. MATERIALS AND METHOD
Molisch
reagent
Add 2 drops of molisch reagent to each
test tubes.
6 test
tubes
Place 2 ml of sample solution (glucose,
sucrose, starch, lactose, fructose, ribose) into
6 separate test tubes.
Cylinder
Get a cylinder, measure 1-2 ml of Conc. H2SO4 and
carefully pour down the side of the test tubes.
Positive result :
Violet ring
Observe.

4. RESULTS
SAMPLE OBSERVATION INFERENCE
Glucose Violet Solution Negative for
Carbohydrates
Sucrose Violet Precipitate Negative for
Carbohydrates
Starch Violet Ring Positive for Carbohydrates
Lactose Violet Ring Positive for Carbohydrates
Fructose Violet Ring Positive for Carbohydrates
Ribose Violet Ring Positive for Carbohydrates

5. RESULTS
GLUCOSE SUCROSE RIBOSE FRUCTOSE LACTOSE STARCH
Violet Ring
Violet Ring
Violet Ring
Violet Ring
Violet Solution
Violet Precipitate

6. Glucose Sucrose
1. Too much concentrated
H2SO4
2. Improper way of adding
concentrated H2SO4
1. Improper drying of test tubes
2. Too much Sucrose solution
According to Voet, (2016):
● excess acid can lead to the
dehydration of glucose
molecules, resulting in the
formation of
hydroxymethylfurfural
(HMF) and other
byproducts
● sulfuric acid can dehydrate
the glucose molecules,
forming furfural, which also
reacts with alpha-naphthol
to give a positive result
According to Voet, (2016):
● moisture in the test tube diluted the
concentration of the sucrose
solution, leading to a weaker
reaction when the reagent is added.
This make it difficult to detect small
amounts of sucrose in the sample.
● excess sucrose may react with the
alpha-naphthol and sulfuric acid to
produce a violet precipitate. This
leads to inaccurate conclusions
about the presence or absence of
carbohydrates in the sample.

7. REFERENCES
Notes on Molisch’s test. (2022, April 4). Unacademy.
https://unacademy.com/content/neet-ug/study-material/biology/
molischs-test/
Vedantu. (n.d.). Molisch’s Test. VEDANTU.
https://www.vedantu.com/chemistry/molisch-test
Voet, D., Voet, J. G., & Pratt, C. W. (2016). Fundamentals of
biochemistry: life at the molecular level (5th ed.). Hoboken, NJ:
Wiley.