Question

Explain coagulation and cataphoresis of colloids.

Answer 1

Coagulation is one of the various properties exhibited by colloidal solutions. A colloid is a heterogeneous mixture of one substance of very fine particles (dispersed phase) dispersed into another substance (dispersion medium). Substances like metals, their sulphides etc. cannot be simply mixed with the dispersion medium to form a colloidal solution. Some special methods are used to make their colloidal solutions. Such kind of sols is known as lyophobic sols. These kinds of colloidal solutions always carry some charges on them. Charge present on the colloidal sols determines their stability. If by any chance we can remove the charge present on the sol, the particles get closer to each other and they accumulate to form aggregates and precipitate under the action of gravity.This process of accumulation and settling down of particles is known as coagulation or precipitation.
Electrophoresis is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field. Electrophoresis of positively charged particles (cations) is called cataphoresis, while electrophoresis of negatively charged particles (anions) is called anaphoresis.