Multimolecular(particle size < 1 nm), they aggregate together and form colloid, e.g. gold sol which is a negatively charged sol.
Sol and its types
Sol is a type of colloid in which solid particles are suspended in a liquid. The particles in a sol are tiny. The colloidal solution displays the Tyndall effect and is stable. Sols may be prepared via condensation or dispersion. Examples of sols include protoplasm, gel, the starch in water, blood, paint, and pigmented ink.
- In lyophilic sols, the dispersed phase particles have a great affinity for the dispersion medium. These are reversible sols. Examples are proteins, rubber etc.
- In lyophobic sols, the dispersed phase particles have no affinity for the dispersion medium. These are irreversible sols. Examples include solutions of metals such as gold and silver.
- The hydrophobic sols are less stable and easily coagulated than hydrophilic sols because hydrophobic sols’ stability is due to charge only. The stability of hydrophilic sols is due to charge and solvation/ hydration.