Bredig's arc method

Bredig's arc method is a method of preparation of colloidal solution, of metals such as gold, silver or platinum.

This method consists of both dispersion and condensation. An arc is struck between electrodes, under the surface of water containing some stabilizing agent such as traces of KOH (potassium hydroxide).The intense heat of the arc vaporizes some of the metal which then condenses under cold water. The water is kept cold as an ice bath.

This method is not suitable when the dispersion medium is an organic liquid as considerable charring occurs.