Requirements
Iodine solution
Methylated spirit/alcohol
Boiling tube
Droppers
Water
White tile
Fresh leaf
Means of heating
Timer
Procedure
Detach a leaf that has been exposed to light for about six hours. This duration ensures that the leaf has photosynthesized.
Put the leaf in boiling water for 10 minutes. This kills the protoplasm, denatures the enzymes and stops any chemical reactions in the leaf.
Remove the leaf and put it in a boiling tube containing methylated spirit or alcohol and boil in a water bath. Methylated spirit is highly ?ammable hence should be boiled indirectly. Boiling with methylated spirit or alcohol decolourises the leaf (removes the chlorophyll).
This ensures that the leaf becomes white so that colour changes can be observed easily when iodine is added.
Remove the leaf and wash off in hot water to remove methylated spirit and to soften the leaf.
Spread the leaf on a white tile and add drops of iodine solution onto the leaf and observe.
Observations
If there is formation of blue black patches on the leaf then starch is present
If the yellow/brown colour of iodine persists on the leaf then starch is absent in the leaf.
Anganifelix answered the question on May 9, 2018 at 09:42
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