Modeling of osmotic kinetics in aqueous solutions, based on experimental data

Osmotic kinetics in aqueous glucose solutions was investigated at two distinct experimental regimes: of constant solution volume and of controlled volume variation. Although osmotic equilibrium is considered to be well understood from thermodynamic viewpoint and does not pose serious ambiguities, the dynamic aspects of the process often exhibit new and even surprising effects, which are difficult to explain within the frames of the traditional kinetic models. Such a non-trivial effect is the appearance of maxima in the rates of solvent transfer, as derived from the obtained kinetic dependence ‘osmotic pressure vs. time’. The attempt to interpret such maxima brought the hypothesis of a polarization effect in the near-membrane space: local dilution of solution, due to the influx of solvent, which in its turn raises a diffusion flux from the bulk. Obviously, at the end (at equilibrium) the concentration should be again homogeneously distributed, after passing through a minimum, which could be the cause for the osmotic rate maxima.