| Abstract
| - Typical custom and commercial hanging mercury dropelectrodes have the geometry of a spherical cap formedby the plane of the lower surface of the electrode holdercutting off the top of the drop. To conduct accuratequantitative measurements by voltammetry, it is necessaryto be able to account for the effects of solution resistance,Ru. A method of determining the solution resistance isproposed and tested. The method involves making measurements of a test reaction (in this case, oxidation offerrocene) by cyclic voltammetry at scan rates whereresistance effects are important and at more than oneconcentration. When the data are analyzed by digitalsimulation, it is found that only one value of Ru willprovide adequate matches between simulation and experiment at all concentrations. An approximate equationhas been derived that allows calculation of Ru from thedimensions of the spherical-cap electrode and the solutionresistivity. The calculated values of Ru for electrodes ofthree different sizes agreed well with the measured values.Error analysis was performed for a particular measurement, the determination of the standard heterogeneouselectron-transfer rate constant, ks, by cyclic voltammetry,and it was shown that uncertainty in Ru puts an upperlimit of about 1 cm/s for the determination of ks with thehanging mercury drop electrodes used in this study.
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