On electro‐osmosis and streaming‐potentials in diaphragms

It is mentioned that the streaming‐potential E/P and the volume of liquid transported by electro‐osmosis v/i are equal, independent of the structure of the diaphragm and independent of its surface conductance. The value of these ratios which, in the absence of surface‐conductance equals ϵζ/4 πηλ diminishes when surface‐conductance is present. This decrease can be accurately taken into account when the diaphragm consists of a single capillary of constant diameter. In the case of real diaphragms, consisting of a network of capillaries of different shape and dimensions the correction factor for surface‐conductance cannot be computed! It has been common practice to estimate the correction factor from the ratio of the observed to the calculated electric resistance of the diaphragm. This procedure is shown to be erroneous, leading to values of the ζ‐potential that are essentially too low.