Practical 3 Investigation of Action of Saliva and Hydrochloric Acid in Two Carbohydrate Solutions
Students are expected to state the objective of this experiment.
Apparatus & Equipments:
Boiling tubes Metal test tube racks Beaker
Graduated plastic dropper Water bath, ~ 37 oC Water bath, ~ 95oC
Carbohydrate solution A Carbohydrate solution B Benedict’s solution
3 M Hydrochloric acid 3 M Sodium hydroxide
1. Prepare two boiling tubes containing 1 ml solution A and 1 ml solution B respectively. Add 1 ml Benedict’s solution to each tube. Heat both tubes together in the (~95oC) water bath for two minutes. Record the results in table 1.
2. Add a few drops of fresh solution A and B separately spaced on a white tile. On each solution, add 1-2 drops of iodine solution. Mix with pen cover. Record your observations in the table 1.
3. Pipette 2 ml solution B into each of four boiling tubes. Label the tubes 1, 2, 3 and 4 respectively near mouth of tube. Label your group name.
4. Place tubes 1 and 2 in a water bath of ~37oC. (It doesn’t matter how long you put it in at this stage as no saliva or HCl have been added yet).
5. Salivate into a small beaker till it reaches about 5 ml.
6. Step (6) and (7) is to be done approximately at the same time. Measure out 4 ml of the saliva prepared in step (4) and pipette 2 ml each into tubes 1 and 4. Shake the contents of the tubes well to ensure thorough mixing.
7. Measure out 4 ml HCl and pipette 2 ml each into tubes 2 and 3.
8. Let tubes 1, 2, 3 & 4 incubate at their respective temperatures (see Table 2) for 35 minutes from this moment.
9. Label 4 more new boiling tubes as follows: 1’, 2’, 3’ and 4’.
10. After 5 minutes of incubation of tubes 1 to 4, pour out…...