Abstract: In a process for production of 1,2-dichloroethane by reaction of chlorine and ethylene at temperatures between about 85.degree. C. and about 160.degree. C. conducted in the presence of a liquid medium in which a recycle stream of 1,2-dichloroethane containing chloroprene and optionally other incompletely chlorinated C.sub.4 hydrocarbons is introduced into the chlorination reaction system, the improvement comprising subjecting the recycle 1,2-dichloroethane to controlled chlorination by contacting it with a chlorination agent in such a manner and under such conditions as to partially chlorinate the chloroprene contained therein to produce a chlorinated derivative thereof, fractionating the thus treated 1,2-dichloroethane to separate chlorinated derivates of chloroprene therefrom, and introducing the thus purified 1,2-dichloroethane recycle into the chlorination reactor.