Theresh Babu Benguluri
Last Activity: 12 Years ago
Aim:
To prepare colloidal solution (sol) of starch.
Principle:
Starch forms a lyophilic sol when water is used as the
dispersion medium. The formation of sol is accelerated by
heating. The starch sol can be prepared by heating starch
and water at about 1000C. It is quite stable and is not
affected by the presence of any electrolytic impurity.
Apparatus required:
? Beaker (250 ml and 50 ml)
Glass rod
? Funnel
? Filter paper
? Mortar and Pestle
? Tripod stand
? Wire – gauze and burner
Materials required:
? Soluble starch (1g) and distilled water. (250 ml)
Procedure:
h. Take 1 g of starch in mortar and add few ml of distilled
water.
i. Grind the starch to make a thin paste and transfer this
paste to a 50 ml beaker. Take about 125 ml of distilled water
in a 250 ml beaker and heat the beaker so that water starts
boiling.
j. Pour the paste slowly with stirring into boiling water in
the beaker
k. Continue boiling for about 2 – 3 minutes and then allow
the beaker to cool
l. Filter the contents of the beaker through a filter – paper,
fixed in a funnel. Label the filtrate ‘Starch Sol’.
Precautions:
c. The apparatus used for preparing sol should be properly
cleaned.
d. Distilled water should be used for preparing sols in
water
e. Starch should be converted into a fine paste before
adding to boiling water.
f. Starch paste should be added in a thin stream to boiling
water.
g. Constant stirring of the contents is necessary during the
preparation of the sol.
7.2 Preparation of colloidal solution (or
sol) of egg albumin