We develop the mass transfer equations for a weak-acid ion exchange membrane in the dusty gas model using the generalised diffusion Stefan-Maxwell equation and the generalized convection-diffusion Stefan-Maxwell equation. Electrical conductivity, hydraulic permeability and water transport number are computed at variable ionization rates of the membrane. The viscous flux is computed from the Carman-Kozeni equation. It is shown that electrical conductivity and hydraulic permeability are the sum of a pure diffusive contribution and of a viscous flow term. The confrontation of experimental, equilibrium and mass transfer results published by Schaetzel and Auclair show that hydraulic permeability can be predicted from electrical conductivity and electroosmotical flux data in the simple diffusion model. For the analyzed experimental results, viscous flow can be neglected, suggesting that the ion exchanger investigated is a dense membrane. The same conclusion can be drawn from the early results published by Despic and Hills.