Preparation of colloid

Preparation of Colloids

A few ways to prepare colloids are given below

•  Chemical method : Colloids can be prepared by chemical reactions leading to formation of molecules by double decomposition, oxidation, reduction or hydrolysis. These molecules then aggregate to form sols 

• Electrical Disintegration/ Bredig’s arc Method: This is applied to obtain colloidal sols of metals like gold, silver and platinum.  An electric arc is stuck between the electrodes of the metal immersed in the dispersion medium. The intense heat produced vapourises the metal, which then condenses to form particles of colloidal size.

• Peptization- It is the process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte. The electrolyte used for this is called peptizing agent. During peptization the precipitate absorbs the one of the ions of the electrolyte on its surface. This causes +veor –vecharge to develop on the precipitate, which ultimately break up into small particles of the size of a colloid.