chronocoulometric constant

symbol: $\cal Q$, unit: $\pu{A s^{1/2} mol-1 m}$

https://doi.org/10.1351/goldbook.09131

Empirically-determined quantity defined by the equation \[{\cal Q} = (1/Ac)\Delta Q/\Delta (t^{1/2})\] where $A$ is the electrode surface area, $c$ is the bulk concentration of the electroactive substance, $Q$ is the charge passed, and $\Delta Q/\Delta(t^{1/2})$ is the slope of a plot of $Q$ against $t^{1/2}$.

Note: The SI unit of $\cal Q$ is $\pu{A s^{1/2} mol-1 m}$.

Source:
PAC, 2020, 92, 641. 'Terminology of Electrochemical Methods of Analysis (IUPAC Recommendations 2019)' on page 670 (https://doi.org/10.1515/pac-2018-0109)