Abstract
The permeability of potassium chloride through the gelatin membrane undissolved by heating is discussed by considering both the velocity of permeation at the membrane surface and permeability inside the membrane. The correlation between the reciprocal of the apparent membrane permeability coeffiicient, defined by the concentration difference, P', and thickness of membrane, L, was found to be linear. The permeability coefficient in the membrane, P*, the velocity of permeation at the interface, k, and the corresponding membrane thickness, L*, expressing resistance at the interface to diffusion, can be calculated from this linear correlation. The difference in the permeation condition affects k but not P*. When k>>2P*/L, the rate-determining process is in the membrane and when k>>2P*/L, the rate determening process is at the interface. Using our apparatus, the mechanism of the membrane permeability for the gelatin membrane is a coupled mechanism. In a thin membrane, the permeation at the membrane interface works as the rate-determining process and the permeation in the membrane takes the place with increasing L. With increasing the gelatin content, KCl permeability in the membrane is reduced and the apparent membrane constant designating its porosity is also reduced. Even if the gelatin content varied, k and L* keep constant.
