What are the major factors of colloidal dispersion
The adsorption of ions by colloidal particles is a major factor in stabilizing a colloidal dispersion, since the colloidal particles in a given system have the same charge they repel each other and hence the tendency to coalesce is reduced. Addition of salts to a sol causes precipitation. Charged particles have strong attraction for the polar water molecules and therefore are hydrated, probably having a complete envelop of water molecules.
Addition of salt helps in the withdrawal of water from the hydrated surfaces of the particles and this helps precipitation. Sols, unlike solutions, have low osmotic pressure. Thus, they cannot pass through animal membranes or through cellulose walls in plants. In lyophobic sols, there is little interaction between the dispersed phase and the dispersion medium. Consequently, properties like viscosity and surface tension of such sols are the same as these of the dispersion medium at the same temperature. In the lyophilic sols, owing to the salvation of the dispersed phase, there is difference in properties. The viscosity of lyophilic sols is greater than that of the dispersion medium and is increased marked by a decrease in temperature or an increase in particle concentration. At particle concentration greater than 20 percent, sols may exhibit elasticity.