The Molisch Test
Shows positive test for:
All carbohydrates. Monosaccharides give a rapid positive test. Disaccharides and polysaccharides react slower.
How to perform the test:
Prepare a solution or suspension of the sample by placing ~0.1 g in 10 ml of water. Two ml of the test solution is placed in a test tube. Two drops of the Molisch reagent (a solution of 
-napthol in 95% ethanol) is added. The solution is then poured slowly into a tube containing two ml of concentrated sulfuric acid so that two layers form.
A positive test is indicated by:
the formation of a purple product at the interface of the two layers.
a negative test (left) and a positive test (right)
As the purple layer is often difficult to see, each of the samples were mixed before the picture was taken. Mixing should be done carefully as large amounts of heat are generated.
a negative test (left) and a positive test (right)