Preparation Of Starch Solution

AIM:
To prepare starch solution.
PRINCIPLE:
Starch sol is easily obtained by mixing starch paste with hot water as it is a hydrophilic colloid.
Being electrically neutral it is quite stable.
APPARATUS:

• 250ml beakers : 2
• Glass rod
• Boiling tube
• Wire gauze
• Tripod stand
• Funnel ( if necessary)

CHEMICALS:

• Soluble starch powder : 1gm
• Distilled water( ordinary pure water may also be used)

SPECIAL PRECAUTIONS:

• The glass apparatus must be clean.
• Starch must be added as a fine paste & never as a powder.
• The fine paste must be prepared with water at room temperature & not with hot water.
• Addition in a thin stream & rigorous stirring are important.

PROCEDURE:

• Take about 100ml water in a 250ml beaker.
• Keep it over a wire gauze on a tripod stand for heating( with a Bunsen burner).
• Take the starch powder in a boiling tube , add some water & make it into a loose paste by shaking well.
• When the water in the beaker has started boiling, pour the starch paste slowly in a thin stream into the boiling water, stirring vigorously with the glass rod.
• After adding the whole paste continue boiling for about 2 minutes.
• Allow the starch sol in the beaker to cool....( Filter if necessary- normally a clear sol will be obtained & there will be no need to filter)..