A SMALL DIFFUSION CELL FOR THE APPLICATION OF THE MULTIPLE MEMBRANE METHOD

Abstract

The multiple membrane method reported by Garvie and Neale to obtain the diffusion coefficient D of penetrant was incorporated in a small diffusion cell to be accommodated in a high pressure cylinder. In the cell, about 20 pieces of thin polymer sheet, each 8mm in diameter, were stacked to build a compact multiple membrane sample, one side of which was exposed, through an open window, to the solution of the penetrant. By using this diffusion cell, Nylon 6 sheet was dyed by p-aminoazo-benzene. Each piece of the component sheet was found to be dyed uniformly to give a distinct circular figure, with monotonically decreasing density from the first membrane. The diffusion profile obtained by a direct measurement of the optical density of each component sheet was exponentially approximated by a function of the type c=c0 exp (βxr). Calculation of D was carried out according to Matano as a function of the concentration of the penetrant. Both D at c/c0=0.5 and D at the concentration of the penetrant which divides the area under the profile into two equal parts were defined. These will be used in our forthcoming researches.