Diffusion of KCl in an amylose film

A method has been developed measuring the diffusion coefficient of KCl in amylose films. The films were soaked in potassium chloride solutions, then immersed in pure water and conductivity measured as a function of time. Different concentrations of the soaking solution were used and the measurements were made at several temperatures. The diffusion coefficient of KCl was found to be independent of the soaking solution KCl concentration, but found to increase with increasing temperature. The diffusion coefficient values were about one quarter of those found in water and varied from 4.8×10⁻¹⁰ to 11×10⁻¹⁰ m² s⁻¹. The activation energy of diffusion was close to that found in water. Two values for the activation energy were obtained, 20.1 and 14 kJ mol⁻¹, indicating a change in the film structure at 45 °C. Amylose films swelled equally in KCl-solutions and water. The thickness of amylose films doubled and the increase in mass was 100–200% corresponding the decrease of amylose content from about 87 to 37%, when the conditions changed from normal humidity conditions to water.