Some new methods for determination of the transport parameters of gases in membranes such as the diffusion coefficient D, the permeability coefficient P and the solubility coefficient S have been proposed. These methods were derived on the basis of more general solutions of the diffusion equations (Fick's first and second laws) for initial and boundary conditions of constant concentration on one side and non-constant initial concentration distribution in the membrane. The results make it possible to set up various independent techniques for the determination of membrane transport parameters from different measured variables such as pressure (or concentration) of penetrant and influx or effusion of penetrant from the permeation cell. These techniques may be useful for the study of membranes for gas permeation processes under different conditions (including condi-tions close to those encountered in industrial operations). Transport parameters in membranes are sometimes deter-mined by a time-lag method. The time-lag solution of the diffusion equations given first by Daynes ' assumes a constant diffusion coefficient and constant concentrations on both sides of the membrane. It is usual'- ' to conduct time-lag experiments in a system that is initially degassed and to cal
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