Process for the separation of mixtures containing m-and p-dichlorobenzene

A process for the separation of dichlorobenzene mixtures containing m- and p-dichlorobenzene in which: (i) the mixture is as an extracting agent contacted with a phosphoric ester of the general formula (I) as an extracting agent in which R1, R2 and R3 are identical or different and represent an aliphatic or cycloaliphatic alkyl or alkenyl radical and R1, R2, and R3 together contain at least 3C-atom and not more than 12 C-atoms, or a mixture of different phosphoric esters (I) of formula or is contacted with a phosphine oxide of the general formula (II) as an extracting agent in which R1, R2 and R3 are identical or different and represent an aliphatic or cycloaliphatic alkyl or alkenyl radical or hydrogen, and R1, R2 and R3 together contain at least 3 C-atoms and not more than 12 C-atoms, or a mixture of different phosphine oxides of formula (II) or a mixture of said phosphoric esters of formula (I) and phosphine oxides of formula (II), and subsequently (ii) the components of the mixture are separated into a m-dichlorobenzene- and a p-dichlorobenzene-containing fraction, and finally (iii) the extracting agent is separated from one of the fractions obtained.