Protocol for Practical Classes
Experiment 6 - Carbohydrates - caracterization
Materials:
Provided by the students :
Paper filters
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From the laboratory starch solution prepared on Experiment 5 4 assays tubes 3 pippetes concentrated sulfur acid– CARE– corrosive bequer |
Molisch test solution Lugol solution Satturated solution of Ammonion sulfate Ethili alcohol (P.A.) |
Metods:
Molisch test:
Tranfer 2 mL of the starch solution to the Tube1 (do not agitate, avoid tranfering the pellet)
Add three drops of the Molisch solution
Add to teh tube 1,2 ml of concentrated sulfur acid (draining it on the tube wall and not dropping it in the middle of the solution)
Write down the result.
Iodine reaction:
Tranfer 2 mL of the starch solution to the Tube2
Add 5mL of distilled water
Add a drop of the Lugol reagente
Warm the Tube 2 to 90oC for 5 min and observe the alterations
Let the Tube in rest to cool and observe the alterations
Write all the results down.
Precipitation reaction (I)
Tranfer 5ml of the starch solution to a bequer (do not agitate)
Add 3ml to the Ammonion sulfate solution to the bequer, while agitating the solution
Let the solution in rest for 10minutes
Filter the solution leaving the pellet in teh bequer
Add 1 drop pf the Lugol reagente to the pellet and another to the filtered material
Write down the results
Precipitation reaction (II)
TRanfer 1ml of the starch solution to the Tube 3
Add 5ml of Ethanol, and agitate ir
Repeat the four last steps of the previous reaction
Write down the results
Objectives :
To understand the mechanism of starch solubilization
To caractherize the starch as a polissacharide
To caractherize the starch monomers
To understand the interaction between starch and Iodine
Report suggestions:
Explain why the starch, besides its polarity, is hardly solubilizates in water under some conditions
Explain how the starch interact with the iodine and how the color changes observed occur.