Process for the continuous preparation of mono- or di-(trichloromethyl)-benzenes

In a process for the continuous preparation of a mono- or di-(trichloromethyl)-benzene, or a mono- or di-(trichloromethyl)-benzene halo-substituted in the benzene ring, from the corresponding unsubstituted or halo-substituted mono- or dimethylbenzene, or said unsubstituted or halo-substituted mono- or dimethylbenzene which is mono- or dihalo-substituted in one or both methyl groups, and chlorine in several steps by irradiating with actinic light, the improvement which comprises reacting said unsubstituted or halo-substituted mono- or dimethylbenzene, or said unsubstituted or halo-substituted mono- or dimethylbenzene which is mono- or dihalo-substituted in one or both methyl groups, in four to 14 steps with chlorine, by introducing chlorine to the second step and the following steps, or to the second and following steps excluding the last step when the quantity of chlorine dissolved in the reaction product amounts to a multiple of the expected conversion, introducing the resulting waste gas to step 1 and reacting the chlorine contained in the waste gas there with fresh said corresponding unsubstituted or halo-substituted mono- or dimethyl benzene, or said unsubstituted or halo-substituted mono- or dimethylbenzene which is mono- or dihalo-substituted in one or both methyl groups.