The Warburg coefficient (or Warburg constant), , is the diffusion coefficient of ions in solution, associated to the Warburg element, . The Warburg coefficient, , also written as, , has the units of The value of can be obtained by the gradient of the Warburg plot, a linear plot of the real impedance 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 can be found by: