Membrane equilibrium

Membrane equilibrium (Donana balance - the balance established between the two solutions separated by a membrane is impermeable for at least one species of ions, located in one of the solutions.
As shown by Donnan (F. D. Donnan), when establishing membrane equilibrium of the diffusion through the membrane electrolyte is distributed on both sides of the membrane unevenly: its concentration in the solution containing non-penetrating ions through the membrane, will be less than in solution on the other side of the membrane. For example, if a plastic bag containing Proteinate sodium, forming ions protein, non-penetrating through a plastic membrane, immersed in a solution of sodium chloride, after the establishment of the membrane equilibrium concentration of sodium chloride in the external solution is more, than in the solution found in a plastic bag. The difference in the concentrations of sodium chloride will be greater, the greater the concentration of Proteinate sodium. Donnan found that when the balance of the work concentrations penetrating (diffusing) ions through the membrane on one side of the membrane should be equal to the product of their concentration on the other side of the membrane.
Membrane equilibrium must be taken into account when considering the membrane permeability, when measuring osmotic pressure in solutions vysokogornyh substances. Membrane equilibrium plays an important role in the distribution of ions between cells and their environment, in the event of biopotentials, swelling of tissues and other