Abstract
When HC1 diffuses into a gelatin gel, the diffusion coefficient (D) is greatly dependent on the concentration of HC1. D is very small when the concentration of HC1 is lower than that of HC1 which saturates a basic group of a gelatin. Above this concentration, D becomes larger than that of HC1 in an aqueous solution. The large D may be caused by ( 1 ) moving of the boundary between a diffusing solution and a gel by swelling or sol-forming of a gelatin gel, or lowering of the gelatin concentration in the gel near the boundary by swelling, ( 2 ) increase in apparent concentration due to further addition of HC1, which is caused by the fixation of HC1 on a basic group in a gelatin gel.
