IUPAC - Ilkovič equation (09139)

Ilkovič equation

https://doi.org/10.1351/goldbook.09139

Equation relating electric current at a dropping mercury electrode under purely diffusional control,

I_{d, t}

, the amount concentration of an electroactive substance at the drop surface

c

, and the concentration in bulk solution

c_{0}

I_{d, t} = - k z F D^{1 / 2} q_{m}^{2 / 3} t^{1 / 6} (c - c_{0})

where

k

is a numerical constant,

z

the electron number of an electrochemical reaction,

F

the Faraday constant,

D

the diffusion coefficient of the electroactive substance,

q_{m}

the mass flux of mercury at the dropping electrode, and

t

the time elapsed from the beginning of the drop.

Notes:

At sufficiently large overpotentials, the surface concentration $c$ will fall to zero, giving a limiting diffusion current. $I_{d, l i m} = k z F D^{1 / 2} q_{m}^{2 / 3} t^{1 / 6} c_{0}$ Mostly, the average current (averaged over drop time and thus drop size) is calculated, when $t$ becomes the drop time $t_{d}$ .
The value of $k$ depends on the units used for quantities in the equation ( $D$ , $q_{m}$ , $t$ , $c$ ), and whether the limiting current or the current averaged over the life of a drop is calculated. For $D$ in ${cm}^{2} s^{- 1}$ , $q_{m}$ in $g s^{- 1}$ , $t$ in $s$ , and $c$ in $mol {cm}^{- 3}$ , the constant $k$ is 708 (limiting current in $A$ ) and 607 (average current in $A$ ).

Source:
PAC, 2020, 92, 641. (Terminology of Electrochemical Methods of Analysis (IUPAC Recommendations 2019)) on page 674 [Terms] [Paper]

Citation: 'Ilkovič equation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.09139 RIS BibTex EndNote

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Ilkovič equation