Visualization of the barrier layer through iontophoresis of ferric ions

The barrier layer in the intact epidermis of pig skin effectively limits the penetration of ferric ions even under conditions of iontophoresis. This was microscopically demonstrated using a ferric ion salt in conjunction with a soluble ferrocyanide to produce a Prussian blue ferric ferrocyanide precipitate. The effectiveness of various skin preparation techniques in breaking through the epidermal barrier layer was examined, utilizing this chemical reaction to stain the skin.