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The validity of the Ilkovǐc equation for polarographic diffusion currents

A. A. Vlček

Czechoslovak Academy of Sciences, Prague


Abstract: It was assumed that these conditions were fulfilled: (1) perfect mobility equil., (2) a soln. completely free of surface-active substances, (3) sufficient excess of the indifferent electrolyte, (4) moderate concn. of the depolarizer, (5) an application of the max.-free system, and (6) use of a capillary of diam. 0.04-0.08 mm. If that assumption was true, the deviations from Ilkovic's equation could be caused by 3 factors: (1) variable current rates during the Hg drop time, (2) neglect of the curvature of the electrode surface, and (3) insufficient exclusion of the turbulent currents. At small dropping speeds, the deviations were caused by the change of the dropping speed during the Hg drop time and by a transfer of the concn. polarization from one drop to the other. This transfer began at the start of the drop formation. At high dropping speeds the disturbing factor was due to the turbulent currents. The development of the current was independent of the drop time. In the presence of the gelatin, the deviations were greater because the concn. polarization transfer was more intensive. Gelatin was disturbing when surface-active substances were present. All the deviations were much higher than assumed if spheric diffusion was neglected. After correcting for the change of dropping speed, the exptl. i vs. t curves for t > 0.1 were in agreement with the theoretical curves of the Ilkovic equation.

Full paper in Portable Document Format: 810a661.pdf (in Czech)


Chemical Papers 8 (10) 661–669 (1954)

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