What chemical do we use to test the presence of starch ?

Explanation

Apparatus required: Tripod stand, beaker, test tube, water, spirit lamp/ bunsen burner, petridish, methylated spirit droper, Iodine.

Procedure:
1) Take a leaf of a plant which has soft thin leaves and well exposed to sunlight.
2) Boil the leaf in methylated spirit over a water bath till it becomes pale -white due to the removal of chlorophyll. Opserve the leaf.
3) Spread the leaf in a dish and add a few drops of tincture iodine / betadine solution on it.
4) Observe the leaf.
Observation : The leaf turned into blue -black colour. It indicate the presence of starch.
Inference : It is proved that leaf has starch, that is formed by photosynthesis.
Precautions :
1) Do not boil the methylated spirit test tube directly on flame.
2) Boil the water bath with low flame.