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I was thinking that different salts used in a salt bridge in a voltaic cell may have different rates of flow of ions in them (perhaps ionic radius or some other property affects the rate?)

I was wondering, if some ions in the salt bridge flow through the solution more quickly, will this have any effect on the overall voltage produced by the cell?

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Voltage measurement is ideally a zero current process. Therefore the details of the ions in the salt bridge and their movements will not be an issue.

In reality, voltmeters do flow some current to measure the voltages. Yet, these currents are so small that in any self-respecting salt bridge, there will not be an issue. If your salt bridge was broken for whatever reason though, then your measurement will be completely incorrect. Most voltmeters will give you an overload in that case.

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    $\begingroup$ I'd point out that modern voltmeters use such high impedance solid state op amp circuits such that there is essentially no current drawn. However in the "olden" days this was not the case with analog voltmeters. I remember the headache of using a Wheatstone bridge to get more precise voltage measurements. So the "good old days" are now! $\endgroup$
    – MaxW
    Jan 28, 2017 at 23:21

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