Hi Horace, Another typo: Frick instead of Fick.
All these macroscopic phenomena you discuss regarding the motion of ions in an electrolyte boil down, at the atomic scale, to the electric force, don't you agree? In any case, in a dense conductor, whether liquid or solid or even a dense gas such as atmospheric air, if you have a _steady_ current of charged particles, then there exists a net DC electric field provoking it, and in the absence of a magnetic field each charged particle does a random walk whose average is the electric field line. Proof: the average velocity (drift velocity) of each charged particle is equal to its mobility times the local electric field, see e.g. http://en.wikipedia.org/wiki/Electron_mobility for the case of electrons, or look up "drift velocity" in the Feynman Lectures on Physics. The electric field between the anode and cathode interfaces of an electrolytic cell may be very small (it's indeed immensely larger in the interface regions), but it explains entirely the steady cell current. Michel 2010/2/24 Horace Heffner <[email protected]>: > > On Feb 23, 2010, at 4:24 PM, Horace Heffner wrote: > >> >> Consider Frick's first law of steady state diffusion, which states the >> flow vector J_i for species i is proportional to the concentration vector (d >> c_i)/( d x) in typical cell conditions, i.e., one dimensionally speaking: >> >> J_i = - D (d c_i)/( d x) >> >> where D is called the diffusion coefficient. > > I accidentally left out a word above: "concentration vector" above should > say "concentration gradient vector". > > > Best regards, > > Horace Heffner > http://www.mtaonline.net/~hheffner/ > > > > >
