Determination of concentration-dependent water diffusivity in a keratinous membrane

A permeation method was developed to determine water diffusivity, D (C), as a function of water concentration (C) in a keratinous membrane. The method involved the determination of a series of mean diffusivities (D) and mean concentrations (C) in the membrane. D was obtained from D = F H(Co - Ch), where F was the flux at steady state, H was the membrane thickness, and Co and Ch were the water concentrations in the membrane at the donor and receptor sides, respectively. The difference between Co and Ch was kept small in each experiment. Therefore, as a first approximation, C was equal to (Co + Ch)/2. After successive approximations, an empirical equation was found to provide the best fit to D versus C and to give the best convergence between the assumed and calculated C; the equation was taken as D(C). D(C) for water in fetal hog periderm was found to be: D(C) = 1.0 X 10(-18) + 9.70 X 10(-9) C0.69.