Oliver Lodges Experiment

Oliver Lodge s Experiment. An experiment first done by the English physicist Oliver Lodge is the origin of a third method by whieh transport numbers can be obtained. Here also there is a limitation one must be able to observe a boundary between two electrolytes, for knowledge of the boundary s movement is the observation upon which the method is based. This implies that the ions concerned must differ in color (not always an easy condition to fulfill) or at least in refractive index (but then the observation of the boundary may not always be easy). 

To understand how this method works, let us have a look at Fig. 4.81. It involves a tube and in this tube there are two solutions and a boundary between them. Let the electrolyte in the upper compartment be named MR and be at a concentration c. The second (bottom) solution is M R, containing the same anion R, but a different cation, M.  

Now a current is passed. The boundary moves and the velocity of that movement u is given by 

One can see that the method would work best with a colored cation, e.g., a cation that 

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