Taking into consideration the possible reactions in the volume of a solution, as well as on the surface of a working electrode, a mechanism responsible for the appearance of electrochemical oscillations has been proposed. It was found experimentally that for the system under study the species H+, HCrO4- and (FeCrO4+)-Cr-III-O-VI ions have a controlling role for the appearance and maintenance of oscillations. Based on the electrochemical reactions found experimentally, a mathematical model able to describe the behavior of the real electrochemical system has been elaborated.