Metal sols are prepared by making electrode of the metals and immersed in dispersion medium and electric arc is struck. This process involves dispersion and condensation.
Bredig’s Arc method
Hydrosols of metals (e.g., platinum, silver, gold) are prepared by this method. The metal electrodes are kept at the two sides of the arc which is enclosed by deionized water. The excessive heat provided by the spark vaporizes some traces of the metal and water gets condensed by vapour. Some amount of KOH is added to water as a stabilizing agent.