The Journal of General Physiology, Vol 9, 97-109,
Copyright © 1925 by The Rockefeller University Press
SOME CONSEQUENCES OF THE THEORY OF MEMBRANE EQUILIBRIA
David I. Hitchcock 1
1 From the Laboratories of The Rockefeller Institute for Medical Research.
In applying Donnan's theory of membrane equilibria to systems where the non-diffusible ion is furnished by a weak acid, base, or ampholyte, certain new relations have been derived. Equations have been deduced which give the ion ratio and the apparent osmotic pressure as functions of the concentration and ionization constant of the weak electrolyte, and of the hydrogen ion concentration in its solution. The conditions for maximum values of these two properties have been formulated. It is pointed out that the progressive addition of acid to a system containing a non-diffusible weak base should not cause the value of the membrane potential to rise, pass through a maximum, and fall, but should only cause it to diminish. It is shown that the theory predicts slight differences in the effect of salts on the ion ratio in such systems, the effect increasing with the valence of the cation.
Accepted on June 26, 1925