Fog is a colloidal solution of

Identify the correct statements from the following :
$I$. Sulphur sol is an example of a multimolecular colloid.
$II$. Tyndall effect is observed when the diameter of the dispersed particles is not much smaller than the wavelength of the light used.
$III$. The process of removing a dissolved substance from a colloidal solution by means of diffusion through a suitable membrane is called peptisation.
$IV$. Eosin,gelatin are examples of negatively charged sols.

Blood can be purified by .......

Why do we add alum to purify water?

The coagulation of $200 \ mL$ of a positive colloid took place when $0.73 \ g$ of $HCl$ was added to it without changing the volume much. The flocculation value of $HCl$ for the colloid is

Which of the following ranges of particle size defines the nano scale?