One desires to prepare a positively charged sol of silver iodide. This can be achieved by

One desires to prepare a positively charged sol of silver iodide. This can be achieved by adding small amount of KI solution to AgNO₃ solution in slight excess . - When KI solution is added to AgNO₃ solution, positively charged sol is formed due to the adsorption of Ag⁺ ions from dispersion medium.

$$\begin{gathered} \mathrm{KI}+{\mathrm{AgNO}}_3(\mathrm{slight} \mathrm{excess})\to \mathrm{AgI}+{\mathrm{KNO}}_3 \\ {\mathrm{AgNO}}_3\to {\mathrm{Ag}}^{+}+{\mathrm{NO}}_3^{-} \\ \mathrm{AgI}\left(\mathrm{s}\right)+{\mathrm{Ag}}^{+}\to \left[\mathrm{AgI}\right] {\mathrm{Ag}}^{+} \end{gathered}$$