A mixing and metering device for mixing and metering liquid chemicals comprises a circulation pump having a suction port and a pressure port, a pipe coil, the contents volume of which is dimensioned such that the chemicals metered into the device have a residence time sufficient for the chemical reaction, a choke tube which guides the circulation stream exiting from the pipe coil, with formation of a choke point, from the outlet of the pipe coil to a metering conduit which is arranged between the choke tube and the suction port of the circulation pump and at least two metering valves, and also a falling tube which is connected to the choke tube and has a vacuum flange for connection of the mixing and metering device to a vacuum device.