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Requesting help with controlled-potential electrolysis

Question asked by Jay Brown on May 9, 2009
Latest reply on May 12, 2009 by rsrodgers

While conducting controlled-potential electrolyses on a zinc metal complex in 0.1 M sulfuric acid, I noticed that my results varied greatly depending upon my selection of the glass frit used to isolate the auxiliary electrode chamber.


If I used a course glass frit, my current vs. time curve was an exponential decay as expected but some of the analyte diffused into the auxiliary electrode chamber.


When I switched to a medium porosity glass frit, less analyte diffusion was noted but the curve was no longer a simple exponential decay. The current first decreased for about 15 minutes and then increased.


Finally, when I used a fine porosity frit, the current no longer decayed at all but actually increased over time.


It probably has to do with an increase in cell resistance, but why would the curve increase over time with the fine porosity frit? I would have expected no change in current over time.


Thank you for your help.