The Warburg coefficient (or Warburg constant; denoted AW or σ) is the diffusion coefficient of ions in solution, associated to the Warburg element, ZW.
The Warburg coefficient has units of
The value of AW can be obtained by the gradient of the Warburg plot, a linear plot of the real impedance (R) against the reciprocal of the square root of the frequency (
This relation should always yield a straight line, as it is unique for a Warburg.
Alternatively, the value of AW can be found by:
where The equation for AW applies to both reversible and quasi-reversible reactions for which both halves of the couple are soluble.
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