The zeta potential is a key parameter that affects the stability of a colloidal system. It is a measure of the electrical charge on the surface of colloidal particles, which can be either positive or negative. The zeta potential plays a crucial role in determining the degree of repulsion or attraction between particles in a colloidal system, which in turn influences the stability of the system.A colloidal system with a high zeta potential either strongly positive or strongly negative is considered stable because the particles experience strong electrostatic repulsion, preventing them from coming close to each other and aggregating. This repulsion keeps the particles dispersed and maintains the stability of the colloidal system.On the other hand, a colloidal system with a low zeta potential close to zero is considered unstable. In this case, the electrostatic repulsion between particles is weak, allowing them to come closer and aggregate. This aggregation can lead to the formation of larger particles, which may eventually settle out of the system, causing the colloidal system to destabilize.The zeta potential can be measured experimentally using a technique called electrophoretic light scattering ELS or laser Doppler electrophoresis. In this method, a colloidal sample is placed in an electric field, causing the charged particles to move towards the oppositely charged electrode. The velocity of the particles is measured using a light scattering technique, such as dynamic light scattering DLS or laser Doppler velocimetry LDV .The zeta potential can be calculated from the measured electrophoretic mobility of the particles using the Henry equation or the Smoluchowski equation, depending on the system's properties. These equations relate the zeta potential to the electrophoretic mobility, the viscosity of the medium, and the dielectric constant of the medium.By measuring the zeta potential of a colloidal system, it is possible to predict and control its stability. Adjusting factors such as pH, ionic strength, or the addition of stabilizing agents can help optimize the zeta potential and improve the stability of the colloidal system.