Charge-wise, the gel-phase water on either side of the membrane behave as a single negatively charged mass. The hydronium ions that are excluded from the gel (analogous to "ionized ice"), are in proportion to the thickness of the gel on either side of the membrane. Since the gel-phase thickness is a colligative property, one that is affected by colloids (mechanism is analogous to freezing point depression), the quantity of hydronium ions on either side of the membrane will differ if the osmolarity (concentration of colloids) differs. When there is osmotic potential across the membrane, i.e., the osmolarity differs, the electrochemical gradient of hydronium ions will push (Greek ōsmos, "push") them across the membrane, and even out the concentration on either side (in balance with the membrane that with its gel-layer on either side act as a single negatively charged mass. ) This will cause a surplus of hydronium ions on the hyperosmotic side and a deficit on the hypoosmotic side (relative to the auto-ionization equilibrium in either compartment that includes the gel-phase), a new equilibrium will be reached (H20 <--> H+ and OH-), and the electrochemical (osmotic) potential continues the osmotic flow across the membrane.
