A process is described for the preparation of very pure 1,2-dichloroethane with heat recovery from equimolar amounts of ethylene and chlorine in 1,2-dichloroethane as solvent in the presence of a tetrachloroferrate(1-) catalyst at a temperature of 75 to 200 DEG C and a pressure of 1 to 15 bar in a reaction zone, which is characterised in that the chlorine gas is dissolved in circulating 1,2-dichloroethane in a mixing zone provided upstream, the ethylene gas is reacted in the reaction zone provided downstream in a finely dispersed liquid phase having a bubble diameter of at most 2.0 mm, this finely dispersed liquid phase is allowed to flow through the reaction zone with a speed of 0.3 to 1 m/s with a residence time of 2.5 to 25 seconds, calculated on the liquid phase, and the very pure 1,2-dichloroethane formed, which contains less than 500 ppm of chlorinated by-products, is withdrawn in the gaseous phase via a flash evaporation. A suitable apparatus for the preparation of very pure 1,2-dichloroethane is composed of a mixer 1 having a chlorine inlet 11, a "static mixer" 2 having an ethylene inlet 5, a flashing vessel 3, a circulation pump 6 and a heat exchanger 7, the mixer 1, the "static mixer" 2, the flashing vessel 3, the circulation pump 6 and the heat exchanger 7 being joined together in a flow-connected manner, the flashing vessel 3 being joined via a throttle valve 4 to a condenser 8, and a product discharge line 9 and an exhaust gas line 10 exiting from the condenser. IMAGE
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