The zeta potential of a colloidal solution is a measure of the electrostatic potential at the slipping plane, which is the boundary between the stationary fluid attached to the particle surface and the mobile fluid in the bulk solution. It is an important parameter that influences the stability of colloidal systems.As the pH of a colloidal solution is varied from acidic to alkaline conditions, the zeta potential changes due to the ionization or deprotonation of functional groups on the surface of the colloidal particles. In acidic conditions low pH , the surface of the particles tends to be protonated, resulting in a positive zeta potential. Conversely, in alkaline conditions high pH , the surface of the particles tends to be deprotonated, resulting in a negative zeta potential.The stability of a colloidal system is affected by the zeta potential because it influences the electrostatic repulsion between particles. When the zeta potential is high either positive or negative , the electrostatic repulsion between particles is strong, preventing them from aggregating and maintaining the stability of the colloidal system. However, when the zeta potential is close to zero, the electrostatic repulsion between particles is weak, making it easier for them to aggregate and potentially causing the colloidal system to destabilize.In summary, the zeta potential of a colloidal solution changes as the pH is varied from acidic to alkaline conditions due to the ionization or deprotonation of functional groups on the particle surface. This change in zeta potential affects the stability of the colloidal system by influencing the electrostatic repulsion between particles. A high zeta potential either positive or negative promotes stability, while a zeta potential close to zero can lead to destabilization and aggregation of particles.