MUTUAL AND SELF-DIFFUSION OF WATER IN GELATIN - EXPERIMENTAL-MEASUREMENT AND PREDICTIVE TEST OF FREE-VOLUME THEORY

Self-diffusion of water in unhardened photographic gelatin is measured by pulsed-gradient nm.r. spectroscopy. Mutual diffusion and activity of water in hardened and unhardened gelatin is measured by step-change gravimetric sorption methods. Predictions of mutual diffusion from the self-diffusion data and published thermodynamic data by using the Vrentas-Duda theory are in agreement with the measured mutual diffusivities. Hardening (i.e. crosslinking) of the gelatin reduces the diffusivity as predicted by an extension to the Vrentas-Duda theory. The water activity increases with crosslinking.