Practical Biochemistry AUST – College of Pharmacy
Lab Report # 2 Student No: 202110395
Title: Qualitative Analysis of Carbohydrates (Disaccharides)
Objective:
1- Identify between aldehydes and ketones
2- Identify carbohydrates
3- Identify reducing sugars
Apparatus: 8 test tubes, test tube rack, bottles, droppers
Glassware: the samples are maltose, sucrose, Molisch (alpha- nephthalon, conc. Sulfuric acid),
Fehling A, Fehling B, Benedict’s reagent and Seliwanoff’s reagent.
Chemicals: the samples are maltose, sucrose, Molisch (alpha- nephthalon, conc. Sulfuric acid),
Fehling A, Fehling B, Benedict’s reagent and Seliwanoff’s reagent.
Procedure:
1- First we wash all test tubes before using them and add to it the test solutions. After washing
them and getting test tube rack, we start with our 4 tests.
2- Molisch test: in this test, we will use 2 out of 8 test tubes and add to each test tube one of
the test solutions (maltose and sucrose).
3- We will be adding about 2ml of each solution to one test tube. Then 3 drops of alpha-
nephthanol and 10 drops of conc. Sulfuric acid.
4- You will see a purple ring between 2 layers for both solutions.
5- Fehling’s test: in this test, we used 2 out of 8 test tubes and added each solution to one of
the test tubes.
6- We will add 4 drops of each test solution to each test tube.
7- Then we add to them 1ml of Fehling A and 1ml of Fehling B and shake the test tubes well.
8- Add both test tubes to the water bath for 3 to 5 minutes and then remove them.
9- You find maltose turn to red brown ppt, while sucrose doesn’t change.
10- Benedict’s test: in this test, we used 2 out of 8 test tubes and added each solution to one of
the test tubes.
11- We will add 1ml of each test solution to one of the test tubes and add to them 2ml of
Benedict’s test.
12- Insert both test tubes in the water bath for up to 3 minutes each, then allow to cool for a bit.
13- For both maltose and sucrose, the solutions will turn to orang red ppt.
14- Seliwanoff’s test: in this test, we used 2 out of 8 test tubes and added each solution to one
of the test tubes.
15- We will be adding 2 drops of each solution to one of the test tubes and about 2ml of
Seliwanoff’s solution to each test tube as well.
16- Add both test tubes to the water bath for 1 minute only, then allow them to cool.
17- For ketose solutions (sucrose), the solution will turn to light pink in color.
18- For aldose solutions (maltose), the solution might change to very light yellow colour or no
change at all (-ve).
Lab Report # 2 Student No: 202110395
Title: Qualitative Analysis of Carbohydrates (Disaccharides)
Objective:
1- Identify between aldehydes and ketones
2- Identify carbohydrates
3- Identify reducing sugars
Apparatus: 8 test tubes, test tube rack, bottles, droppers
Glassware: the samples are maltose, sucrose, Molisch (alpha- nephthalon, conc. Sulfuric acid),
Fehling A, Fehling B, Benedict’s reagent and Seliwanoff’s reagent.
Chemicals: the samples are maltose, sucrose, Molisch (alpha- nephthalon, conc. Sulfuric acid),
Fehling A, Fehling B, Benedict’s reagent and Seliwanoff’s reagent.
Procedure:
1- First we wash all test tubes before using them and add to it the test solutions. After washing
them and getting test tube rack, we start with our 4 tests.
2- Molisch test: in this test, we will use 2 out of 8 test tubes and add to each test tube one of
the test solutions (maltose and sucrose).
3- We will be adding about 2ml of each solution to one test tube. Then 3 drops of alpha-
nephthanol and 10 drops of conc. Sulfuric acid.
4- You will see a purple ring between 2 layers for both solutions.
5- Fehling’s test: in this test, we used 2 out of 8 test tubes and added each solution to one of
the test tubes.
6- We will add 4 drops of each test solution to each test tube.
7- Then we add to them 1ml of Fehling A and 1ml of Fehling B and shake the test tubes well.
8- Add both test tubes to the water bath for 3 to 5 minutes and then remove them.
9- You find maltose turn to red brown ppt, while sucrose doesn’t change.
10- Benedict’s test: in this test, we used 2 out of 8 test tubes and added each solution to one of
the test tubes.
11- We will add 1ml of each test solution to one of the test tubes and add to them 2ml of
Benedict’s test.
12- Insert both test tubes in the water bath for up to 3 minutes each, then allow to cool for a bit.
13- For both maltose and sucrose, the solutions will turn to orang red ppt.
14- Seliwanoff’s test: in this test, we used 2 out of 8 test tubes and added each solution to one
of the test tubes.
15- We will be adding 2 drops of each solution to one of the test tubes and about 2ml of
Seliwanoff’s solution to each test tube as well.
16- Add both test tubes to the water bath for 1 minute only, then allow them to cool.
17- For ketose solutions (sucrose), the solution will turn to light pink in color.
18- For aldose solutions (maltose), the solution might change to very light yellow colour or no
change at all (-ve).
