In the presence of impermeant ions, there is an unequal distribution of the permeant ions across the semipermeable membrane. This is called as the Gibbs-Doron effect. In medical physiology, we discuss this effect under two different topics. The first is to explain the concentration difference between the plasma and the interstitial fluid. The plasma protein is the impermeant solid here. Though the sodium and chloride are freely permeable across the capillary membrane, they do not have a equal distribution. The concentration of sodium is higher in the plasma because of electrostatic attraction by the anionic protein. The concentration of chloride is slightly lower in the plasma as compared to the interstitial fluid. That is because of electrostatic repulsion by the anionic proteins. At equilibrium, the product of permeant ions on one side is equal to the other side. This equilibrium is called as Gibbs-Doron equilibrium. At equilibrium, there is an electron neutrality which means the total number of positive ions and the negative ions on each side is equal. Each side have net charge of zero. The product of permeant ions on both sides is equal. This also can be rewritten as Gibbs-Doron ratio. At equilibrium, there will be greater number of ions in the side with impermeant ions. This will result in an osmotic gradient. This Gibbs-Doron equilibrium is not a true equilibrium because of the presence of osmolar gradient. Gibbs-Doron equilibrium also causes a development of potential difference across a lipid bilayer. The lipid bilayer acts as a capacitor which stores charges which is responsible for this potential difference. I have made a detailed video on how Gibbs-Doron effect can cause formation of membrane potential. I have given the link in the description. Please watch that. The redistribution of ions by Gibbs-Doron effect cannot fully explain the concentration gradient existing in the cell or the magnitude of the resting membrane potential in a cell. Some estimates show that Gibbs-Doron equilibrium alone may produce a membrane of about minus 20 millivolts. The passive redistribution of ions by this effect is not the only reason behind the concentration gradient. The concentration gradient in the cell or maintained by active transport mechanisms like sodium potassium aty-pace. The resting membrane potential is an active steady state and not a passive equilibrium. The magnitude of the resting membrane potential is best understood by studying the known potential and the Goldman equation and that's our next topic. Thank you.