What textbook states about the formation of electric double layer:
When silver nitrate solution is added to potassium iodide solution the precipitated silver iodide adsorbs iodide ion from dispersion medium and negatively charged colloidal solution results. Having acquired a negative charge by selective adsorption on the surface of colloidal particles, this layer attracts counterion from the medium forming second layer. The combination of these two layers of opposite charge is called Helmholtz electrical double layer. The first layer of ions is firmly held and termed as fixed layer while second layer is mobile and termed as diffused layer.
Reference : chapter 5; page :141 http://ncertbooks.prashanthellina.com/class_12.Chemistry.ChemistryI/index.html
What I understand about electrical double layer by browsing various internet sources is:
An electric double layer consists:
Surface charge: charged ions adsorbed on the surface of the colloidal particles or intrinsic surface charge or through loss or gain of electrons as in case of electrodes.
Stern layer (fixed layer): counterion attracted to particle surface and closely attached to it by electrostatic forces.
Diffusion layer: a film of dispersions medium adjacent to the particle containing higher concentration of counterion due to the residual electrostatic forces from the charged colloidal particles.
Is my understanding correct? Does the textbook statement means something more or do I miss something? I like to have a almost clarified understanding about the electric double layer.