The electrochemical behaviour of mixtures of several iron(II) and iron(III) compounds was studied in acidic media at a carbon paste electrode. Voltammetric techniques were used to obtain electrochemical spectra of these mixtures which were interpreted in order to elucidate the nature of their electrochemical transformations. Appropriate limited potential scans were used to verify the identity of the different chemical species involved in the electrochemical reactions. Finally, the electrochemical behaviour of magnetite was investigated and a theoretical explanation of the different processes was proposed based on its crystallographic structure.