Abstract
Diffusion coefficient D of Chrysophenine G (C. I. Direct Yellow 12) (DY 12) in cellophane (CELL.) was obtained by the multiple membrane method and under high hydrostatic pressures up to 2.5kbar. The pressure dependence of D was analysed and discussed in terms of the activation volume ΔV_??_ for diffusion obtained by where R, T and P are the gas constant, the absolute temperature and the pressure, respectively. The pressure effect was not large at 100°C, where ΔV_??_ was found to be 18cm3/mol. This amount was only 4% of the effective volume of DY 12, 430cm3/mol. Based on the free volume theory, it was concluded that CELL, was swollen with water and the mean free volume in the initial state was almost sufficient to accommodate the diffusing penetrant, i.e., a large local volume expansion by fluctuation was not needed for activation.
