Starch

1) Detection with Iodine

Required: 1,5% starch-solution; Lugol`s solution ( a tincture of iodine); t.-t.

Add to a few [ml] of starch-solution 3-4 drops of Lugol's solution and shake. Warm carefully and allow to cool.
Observations?


2) Fehling-Test

Try Fehling's test with starch-solution.
Conclusion?


3) Transformation to Dextrins

Required: starch; Lugol's solution

Give two spatula of starch into a test-tube and warm carefully. Do not carbonize it ! - After cooling add 2 pipettes of water to the yellowish substance. Shake! - Finally add ca. 3 drops of Lugol ' s solution .
Observations?


4) Hydrolysis by acid

Required: 1,5 % starch-solution; dil. hydrochloric acid; dil. sodium hydroxide-solution; Lugol`s solution; GOD-paper; conical flask; BB; tripod; asbestos wire

Procedure:

Give into a conical flask 20 [ml] of starch-solution and add one pipette of dil. HCl (acid). Heat until boiling.
From now on you take every 3 minutes one pipette from the mixture and give it into a test-tube. Add another 2-3 pipettes of water to it and finally dropwise Lugol`s solution.
Count the number of drops in the first experiment and use exactely the same number of drops for the following ones ! The whole experiment is finished if you obtain a yellow solution.
Addition: Neutralize the last yellow solution with sodium hydroxide-solution and make the GOD-test. Try also the resorcin-­test.
Observations? - Explanations?



Cellulose

5) Hydrolysis by acid

Required: cottonpads or filter paper; conc. sulfuric acid; sodium hydroxide-solution; Fehling-solution I + II; GOD-paper; pH-paper; mortar and pestle; small beaker; t.-t. and -holder; BB; tripod and asbestos wire

Procedure:

Give into a mortar a cotton pad (or a filter paper). Add with a pipette a small amount of conc. sulfuric acid (Danger!) and grind with a pestle until you obtain a liquid pulp. Carefully dilute with ca. 6 pipettes of water. Boil for ca. 5 minutes in a beaker and refill evaporated water. Neutralize with sodium hydroxide-solution.
Try with that solution the GOD- and the Fehling-test!

Observations? - Explanations?