Facilitated gas transport in membranes is a diffusion/reaction system in which at least one reactant is spatially confined. Despite longstanding interest in this process, the consequences of spatial constraint have generally been overlooked. They are examined here in the cases of transport of the acid gases CO2, H2S, and SO2 in Solutions of alkali and of ethylene in solutions of silver salts. Diffusion potentials are shown to be significant in each case, playing a role that complements spatial constraints. Nonetheless, at least in the ethylene case, fluxes calculated using an analysis that enforces spatial constraints but neglects ionic interactions are indistinguishable from those generated by an analysis that accounts for both.