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 th e self-diffusion data and published thermodynamic data by using the Vr entas-Duda theory are in agreement with the measured mutual diffusivit ies. Hardening (i.e. crosslinking) of the gelatin reduces the diffusiv ity as predicted by an extension to the Vrentas-Duda theory. The water activity increases with crosslinking.