CBSE Class 12-science Answered

This method is used to prepare Sols of metals such as Platinum, Silver, Copper or Gold. The metal whose sol is to be prepared is made as 2 electrodes immersed in dispersion medium such as water. The dispersion is kept cooled by surrounding it with a freezing mixture. An electric arc is struck between the electrodes. This creates tremendous heat generated by the arc vapourises the metal which are condensed immediately to liquid to give a colloidal solution. This Colloidal solution  is stabilized by adding small amount of KOH to it.