The investigated reactor is a laboratory-scaled tubular reactor designed by Fraunhofer IMM and manufactured by 3D laser melting for the formation of organomagnesium halide reagents. Figure displays the reactor in more detail. It consists of a reactor cartridge and a replenishment unit that can be attached to the main reactor body for replenishing metal turnings during organometallic halide reagent synthesis. Since the reactor is used for Grignard reagent synthesis, the residence time measurements are performed by utilizing a reactor cartridge filled with magnesium turnings. Although the reactor cartridge including the magnesium packing is used for the synthesis of magnesium-based organometallic halide reagents and, as a result, the magnesium packing is being subject to continuous change during synthesis, the actual state of the magnesium bed at the beginning of a synthesis is used to determine the residence time distributions, i.e., without taking synthesis into account.