General Physical Properties of Colloidal Solutions
The important properties of colloidal solutions are described below.
General Physical Properties
(i) Heterogeneity: Colloidal solutions are heterogeneous in nature and consist of two phases-dispersed phase and dispersion medium.
(ii) Visibility of dispersed particles: Although colloidal solutions are heterogeneous in nature, yet the dispersed particles present in them are not visible to the naked eye and they appear homogenous. This is because colloidal particles are too small to be visible to the naked eye.
(iii) Filterability: Due to very small size, the colloidal particles pass through an ordinary filter paper. However, they can be retained by animal membranes, cellophane membrane and ultrafilters.
(iv) Stability: Lyophilic sols in general and lyophobic sols in the absence of substantial concentrations of electrolytes are quite stable and the dispersed particles present in them do not settle down even on keeping. However, on standing for a long time, a few colloidal particles of comparatively larger size may get sedimented slowly.
(v) Colour: The colour of a colloidal solution depends upon the size of colloidal particles present in it. Larger particles absorb the light of longer wavelength and therefore transmit light of shorter wavelength. For example, a silver so having particles of size 150nm appears violet, whereas that having particles of size 60nm appears orange yellow.