Preparation of Sols

Sols are those colloidal systems where a solid is dispersed in liquid. Sols have also been classified as lyophobic colloids. Lyophobic sols cannot be prepared by simple mixing of dispersed phase and the dispersion medium. Two special techniques are employed for the preparation of lyophobic colloids: broadly classified as ‘top-down ’ or ‘dispersion ’ methods and ‘bottom-up ’ or ‘condensation ’ methods. In ‘top-down ’ or ‘dispersion ’ methods, larger macro-sized particles are broken down to colloidal size. On the other hand, in ‘bottom-up ’ or ‘condensation ’ methods particles of colloidal size are produced by aggregation of atoms, ions or molecules. We shall follow the ‘bottom-up’ or ‘condensation’ method to prepare Fe(OH)3 colloid.