All solvents and reagents are used without further purification: magnesium turnings (coarse: Merck KGaA, fine: Almamet GmbH), tetrahydrofuran (> 99.9 %, p.a.,Th. Geyer GmbH & Co. KG), toluene (≥ 99.7 %, Honeywell International Inc.). The following pumps are used: Postnova syringe pump with 2.5 mL Hamilton glass syringes, Landgraf syringe pump with a syringe size depending on amplitude and frequency to achieve (B. Braun Melsungen GmbH), HNP micro annular gear pump, Ismatec valveless rotary piston pump. Further details on the specific pumps are mentioned in table 1. A Matrix-MF infrared (IR) spectrometer with diamond micro ATR probe from Bruker Optik GmbH is used for concentration measurements. Experimental data are recorded using the software OPUS (version 6.5, Bruker Optik GmbH). The residence time measurements are conducted by using the displacement marking method (step function), in which a tracer-free inlet flow is exchanged for a tracer-containing flow (or vice versa) of the same size at time t=0. Toluene was selected as the tracer substance (toluene peak at 732 cm -1 ), since it does not react with the magnesium metal and can be used as a solvent in Grignard reagent synthesis as well. investigations (see part 2), the tracer must also behave inertly towards the chemicals used in Grignard reagent synthesis and in particular towards the Grignard reagent itself, and the chosen analytics in terms of hardware and software must not be affected in a negative way by the chemicals.