The addition of an electrolyte can significantly affect the stability of a colloidal dispersion. A colloidal dispersion consists of small particles colloidal particles dispersed in a continuous medium. The stability of a colloidal dispersion is determined by the balance between attractive and repulsive forces between the colloidal particles. Electrostatic repulsion between the particles, caused by the presence of charged groups on their surfaces, is the primary factor that prevents the particles from aggregating and maintains the stability of the dispersion.When an electrolyte is added to a colloidal dispersion, it dissociates into its constituent ions. These ions can interact with the charged groups on the surface of the colloidal particles, leading to a reduction in the electrostatic repulsion between the particles. This phenomenon is known as "screening" or "shielding" of the surface charges.The underlying principle behind this effect is the Debye-Hückel theory, which describes the distribution of ions around a charged particle in an electrolyte solution. According to this theory, the addition of an electrolyte increases the ionic strength of the solution, which in turn reduces the thickness of the electric double layer surrounding the colloidal particles. As the thickness of the electric double layer decreases, the electrostatic repulsion between the particles is reduced, making it easier for them to come closer and aggregate.The extent to which the addition of an electrolyte affects the stability of a colloidal dispersion depends on several factors:1. Concentration of the electrolyte: Higher concentrations of electrolytes lead to a greater reduction in electrostatic repulsion and a higher likelihood of particle aggregation.2. Valency of the electrolyte ions: The valency of the ions in the electrolyte plays a crucial role in determining the extent of charge screening. Ions with higher valency are more effective in reducing the electrostatic repulsion between the colloidal particles. This is known as the Schulze-Hardy rule.3. Particle size and surface charge density: Smaller particles with higher surface charge density are generally more stable in the presence of electrolytes, as they have a greater electrostatic repulsion to overcome.4. Type of colloidal particles and the continuous medium: The nature of the colloidal particles e.g., hydrophobic or hydrophilic and the continuous medium e.g., polar or non-polar can also influence the stability of the dispersion in the presence of electrolytes.In summary, the addition of an electrolyte to a colloidal dispersion can reduce the stability of the dispersion by decreasing the electrostatic repulsion between the particles. The extent of this effect depends on the concentration and valency of the electrolyte ions, as well as the size, surface charge density, and nature of the colloidal particles and the continuous medium.