Osazone test is performed to differentiate the reducing sugars on the basis of crystal formation.
REAGENTS:
1. Phenylhydrazine mixture consisting of:
i. Phenylhydrazine, and
ii. Anhydrous sodium acetate.
2. Original solution (0.8.) – containing a carbohydrate
PRINCIPLE:
Aldehyde or keto group containing sugars reacts with the amine group of phenylhydrazine to give phenylosazone.
PROCEDURE:
- Take phenylhydrazine mixture and till about half an inch of the test tube with it.
- Add 3 to 5ml of sugar solution (original solution) to the test tube.
- Mix thoroughly and place it in a boiling water bath.
- Note the appearance of a yellow crystalline precipitate in the test tube.
- Remove and allow the test tube to cool slowly.
- Do not cool the test tube under tap water.
- Examine the crystals under the microscope and make a drawing.
- Draw only what you see.
NOTE:
Osazones of glucose are formed in 10-15 minutes whereas those of disaccharides take up to 45 minutes. Sucrose does not react with phenylhydrazine to form crystalline compounds called osazones.
Observation and Result:
| SUGAR | OSAZONE | SHAPE |
| Glucose | Glucosazone | Needle-shaped |
| Fructose | Fructosazone | Needle-shaped |
| Galactose | Galactosazone | Fluffy ball shaped |
| Lactose | Lactosazone | Fluffy ball shaped |
| Maltose | Maltosazone | Sunflower shaped |
Precautions:
- Wash the apparatus before and after the experiment.
- Carefully Observe the Crystals under the microscope.
- Carefully handle all the chemicals.
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