Transient-state transport in some finite systems .3. Some historical and hitherto largely-unexplored aspects of time-lag theory

With reference to the pioneering papers of Daynes (1920) and of Barrer (1939), expressions have been derived for time-lags associated with transport through a slab membrane when an arbitrary initial distribution of diffusant is present. The treatment relates to a constant diffusion coefficient with solution or sorption obeying Henry's law. Three methods of evaluating the time-lag are presented in the chronological sequence in which they were developed. Some concentration and position dependencies of the time-lags have been investigated with particular reference to initial distributions of diffusant attainable in practice.