Digital Interactive Content Cells Visking/dialysis tubing experiment Observe the movement of substances, iodine and starch, across the membrane of a Visking or dialysis tubing. Iodine solution turns from yellowish-brown to dark blue when it comes into contact with starch. https://videos.files.wordpress.com/Dhx9Ac0v/dialysis-tubing-diffusion-time-lapse_hd.mp4