For instance, losing an order of magnitude in diffusion coefficient for ions when the system is acetylated reduces the characteristic diffusion length L by a factor of between 3 and 4, as the distance a particle diffuses in a given time is proportional to the square root of the diffusion coefficient and time . Thus, the penetration over an hour of solution uptake would be expected to be 3 times less for acetylated wood, at least for small monovalent cations.