A mathematical model for electrohydrodymanic impedance was developed in which hydrodynamic and convective diffusion equations were coupled by a relationship between viscosity and concentration. This procedure allows better understanding the physical problem separating the mass transport and the hydrodynamic effects and the model fit to previously reported experimental results revealed a larger viscosity gradient than previously inferred: These results are consistent with the hypothesized formation of a colloidal suspension of ferrous sulfate particles. (C) 2015 The Electrochemical Society. All rights reserved.