Effect of medium viscosity in a closed unstirred Belousov–Zhabotinsky system

Complex periodic and aperiodic behaviors are reported in an unstirred Belousov–Zhabotinsky oscillatory reaction containing different concentrations of polyethylene-glycol. A route from chaos following an inverse Ruelle–Takens–Newhouse (RTN) scenario is identified. Thus, hydrodynamic effects, being mainly convective, seem to be responsible for the observed RTN scenario. We demonstrate that the medium viscosity, namely the polyethylene-glycol concentration, is a bifurcation parameter for the sequence chaos → quasi-periodicity → period-1.