There is difficulty in attaching a precise meaning to the term "aperiodic component" in the context of a.c. voltammetry. Once this difficulty is circumvented, it becomes possible to use a filter or Fourier processing to model the dependence of the aperiodic component of the reversible current, and its semiintegral, on the various electrical parameters: d.c. potential, d.c. scan rate, a.c. frequency, and a.c. amplitude. No particular utility has been ascribed to the aperiodic current, but its semiintegral can provide information similar to that of d.c. linear-scan voltammetry. Experiments with the hexammoniaruthenium(III) cation provide confirmation of the theory and allow determination of the ion's diffusivity and the halfwave potential of its reduction. (c) 2014 Elsevier B.V. All rights reserved.