Sol (colloid)

A sol is a colloidal suspension made out of tiny solid particles[1] in a continuous liquid medium. Sols are stable and exhibit the Tyndall effect, which is the scattering of light by the particles in the colloid. Examples include amongst others blood, pigmented ink, cell fluids, paint, antacids and mud.

Artificial sols can be prepared by two main methods: dispersion and condensation. In the dispersion method, solid particles are reduced to colloidal dimensions through techniques such as ball milling and Bredig's arc method. In the condensation method, small particles are formed from larger molecules through a chemical reaction.

The stability of sols can be maintained through the use of dispersing agents, which prevent the particles from clumping together or settling out of the suspension. Sols are often used in the sol-gel process, in which a sol is converted into a gel through the addition of a crosslinking agent.

In a sol, solid particles are dispersed in a liquid continuous phase, while in an emulsion, liquid droplets are dispersed in a liquid or semi-solid continuous phase.

Properties of a Colloid (applicable to sols)

• Heterogeneous Mixture
• Size of colloid varies from 1 nm - 100 nm
• They show the Tyndall effect
• They are quite stable and hence they do not settle down when left undisturbed