The miniaturized experimental cell (Figure ) developed in a collaborative study is based on a classical through-diffusion technique, where two large reservoirs (50 ml each), filled with aqueous solutions, are connected by a glass capillary filled with a silica-gel porous medium. In this setup, the capillary is 8 cm long, has a wall thickness of 0.02 mm, an inner diameter (ID) of 0.3 mm, and is connected to the reservoirs through two tapered ends with an ID of 3 mm. The silica-gel was directly formed in the capillary by mixing a 1N HCl solution with a 5% diluted Na2SiO3 solution .