Like gum and egg albumin, starch forms a stable hydrophilic sol. However, the preparation is carried out with boiling water for better and quicker dispersion of starch into water.
To prepare a sol of starch
(i) Grind the starch in the mortar with the help of pestle. Add a little distilled water to make a thin paste of the starch.
(ii) Take about 100 mL of distilled water in a 250 mL beaker and heat it to boiling.
(iii) Add the paste of the starch into the boiling water along a glass rod and keep on stirring constantly with the glass rod.
(iv) When the addition of the paste is complete, boil the contents of the beaker for further 5 minutes.
(v) Allow the beaker to cool down to room temperature and then filter. The filtrate is the required sol of starch.