To ensure comparability between the results, a net volumetric flow rate of 2 mL/min toluene/THF solution was maintained in the results presented here. This volumetric flow rate was generated by means of a pulsation-free micro annular gear pump (pump C). In the case of the fine magnesium turnings, an additional valveless rotary piston pump (pump D) ensured the oscillation of the volume flow. In the case of coarse magnesium turnings, the programmable syringe pump (pump B) was used to generate the oscillation. The maximum amplitudes and frequencies that can be achieved depend on the pump used and its technically possible operating conditions (table ).