Comparison of Diffusion Coefficients Measured Electrochemically and Non-Electrochemically

Diffusion coefficients of Co(en)3I3⋅H2O, FeCl3, and K3Fe(CN)6 were measured using the methods of polarography, chronopotentiometry, and diaphragm cell for the purpose of determining any relationships which may exist between these values. A major objective of the present study was to relate diffusion coefficients obtained by a simple non-electrotrochemical method to diffusion coefficients used in electrochemical techniques. It was found that the polarographically determined diffusion coefficients were all 1.04 times larger than the chronopotentiometric values. This constant factor is probably due to viscosity differences tn the polarographic and chronopotentiometric solutions though instrumentation differences may play a part. Comparison of the diffusion coefficients determined electrochemically with the diaphragm cell values indicates a relationship between the two quantities. A smooth curve of electrochemical diffusion coefficients plotted against those obtained from the diaphragm cell appears to exist, but due to an uncertainty of the diaphragm cell values for Co(en)3I3⋅H2O this could not be verified unequivocally