When a freshly precipitated substance is converted into a colloidal solution with the help of a third substance, the process is known as

Peptization

The correct answer is 2. peptization.

Peptization is the process of converting a freshly precipitated substance into a colloidal solution with the help of a third substance called a peptizing agent. The peptizing agent adsorbs on the surface of the precipitate and breaks up the aggregates of particles, making them smaller and more dispersed. This allows the particles to remain suspended in the dispersion medium and form a colloidal solution.

Coagulation is the process of converting a colloidal solution into a precipitate. Electrodispersion is the process of dispersing a solid in a liquid by applying an electric field. Dialysis is the process of removing small molecules from a solution by diffusion through a semipermeable membrane.

Therefore, the process of converting a freshly precipitated substance into a colloidal solution with the help of a third substance is called peptization.