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In the attached polarogram from Heyvrovsky's 1959 Nobel lecture, transitions from one plateau to the next are smoothened out rather than sharp and abrupt. Why is that?

I understand that currents were small in this experiment, so metal ion concentrations should not change significantly.

I would have expected the current to jump from one level to the next as soon as the necessary voltage is reached. What broadens these transitions?

https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1959/heyrovsky-lecture.pdf

Heyvrovsky polarogram

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  • $\begingroup$ Related question: Polarography is less popular nowadays than it used to be, but can anyone point me to contemporary applications / results that I could show my students? $\endgroup$ – Martin Jun 18 '18 at 9:39
  • $\begingroup$ Before actually reaching the reduction potential, reduction of the metal ions happens only in very tiny amounts, but eventually becomes measurable as the equilibrium constant approaches 1 from below, (e.g. 0.001 → 0.01 → 0.1 → 0.5 → ...). I discuss something similar in this question. $\endgroup$ – Nicolau Saker Neto Jun 18 '18 at 12:32

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