Fick’s Diffusion Experiments Revisited —Part II (English Translation of Fick’s Orginal Thinking)

In this paper, we revisit Fick’s original diffusion experiments and reconstruct the geometry of his inverted funnel. In Part I, we show that Fick’s experimental approach was sound and measurements were accurate despite his own claims to the contrary. Using the standard modern approach, we predict Fick’s cylindrical tube measurements with a high degree of accuracy. We calculate that the salt reservoir at the bottom of the inverted funnel must have been about 5 cm in height and the unreported depth of the deepest salt concentration measurement by Fick was yet another 3 cm above the reservoir top. We verify the latter calculation by using Fick’s own calculated concentration profiles and show that the modern diffusion theory predicts the inverted funnel measurements almost as well as those in the cylindrical tube. In Part II, we provide a translation of Fick’s discussion of diffusion in liquids in the first edition of his three-volume monograph on Medical Physics published in 1856, one year after his seminal Pogendorff’s Annalen paper On Diffusion.