In order to analyze the fields of existence of the chaotic region as a function of initial concentration in a closed unstirred cerium catalyzed Belousov–Zhabotinsky system, a large number of experiments were carried out, varying the relative quantities of the three principal reactants (malonic acid, potassium bromate and cerium(IV)). A ternary bifurcation diagram is shown as a function of the percentage in volume of the three initial concentrations of reactants. Chaotic, quasi-periodic, periodic and no oscillations regions are clearly demonstrated.