Perform the osazone test on the given sugars and identify them from the crystal shapes.

1. 1 · Aim. To prepare the osazones of the given sugars and identify each sugar from the time of formation and crystal shape.
2. 2 · Principle. A reducing sugar reacts with three molecules of phenylhydrazine at carbons 1 and 2 to form a yellow osazone. Each sugar gives a typical crystal shape; disaccharide osazones are soluble while hot.
3. 3 · Requirements. Sugar solutions, phenylhydrazine hydrochloride with sodium acetate, glacial acetic acid; boiling water bath, slides, coverslips, microscope; gloves and goggles.
4. 4 · Procedure.
   • 5 mL sugar + about 0.5 g phenylhydrazine mixture + 5 drops glacial acetic acid; warm to dissolve.
   • Boiling water bath; note the time crystals appear.
   • After 30-45 minutes, cool slowly in air.
   • View a drop under low power and draw the crystals.
5. 5 · Observation. [Draw: needles (glucose, fructose), sunflower (maltose), powder-puff (lactose), with time of formation]
6. 6 · Result. Needles in about 2 min: fructose; needles in about 4-5 min: glucose; sunflower on cooling: maltose; powder-puff on cooling: lactose.
7. 7 · Precautions. Gloves (phenylhydrazine is toxic), cool slowly, heat all tubes together and note the time, never pipette by mouth.

Scoring tip: Neat, labelled drawings of the crystals carry most of the marks. Always write the time of formation next to each shape.