Analytical tests of glycerol - Acrolein and Dunstan test
(a) Acrolein test: while glycerol is heated with an extremely offensive smell is generated due to formation of acrolein. Its aqueous solvent restores the colour of schiff's reagent and decreases Fehling solution and Tollen's reagent.
(b) Dunstan's test: A drop of phenolphthalein is added almost 5 ml of borax solution. The pink in colour seems on adding 2-3 drops of glycerol, pink colour goes. The pink colour emerges out on heating and disappears on cooling again.