When an excess and a very dilute aqueous solution of $\mathrm{Kl}$ is added to a very dilute aqueous solutions of silver nitrate, the colloidal particles of silver iodide which are associated with the Helmholtz double layer

When$\mathrm{KI}$ solution is added to ${\mathrm{AgNO}}_3$ solution, positively charged sol results due to adsorption of ${\mathrm{Ag}}^{+}$from dispersion medium forming $AgI\mid A{g}^{+}$acquired a positive charge. This layer attracts counter ions from the medium forming a second layer as $4gI\left|{\mathrm{Ag}}^{+}\right|I^{-}$.