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)