Abstract:
One of the most fundamental of irreversible processes is that of diffusion, by which a difference of concentration is reduced by the spontaneous flow of matter. In a solution containing a single solute, the solute moves from the region of higher concentration to that of lower concentration while the solvent moves in the opposite sense.
The theory of diffusion has been developed both on a three dimensional model Harned, Chem. Rev., 40, 462, (1947) and a one dimensional model Robinson & Stokes, "Electrolyte Solutions", Butterworths Scientific Publications, London, (1959). Since there is no loss in generality by restriction to one dimension all considerations hereafter shall be confined to the latter case.
The flux, J, is defined as the amount of material crossing unit area of a given plane perpendicular to the direction of flow per unit time.
