The invention relates to a process and a device for the dissolution of salt that is hardly soluble, especially sodium chloride and other poorly soluble salts in 1,2 dichloroethane, which primarily are to be used in direct chlorination plants for the production of 1,2 dichloroethane. This aim is achieved by mounting an ultrasonic transducer (sonotrode) in the dissolution chamber which is filled with a suspension of salt crystals and 1,2 dichloroethane. The suspension is sent through a filter upon dissolution of the salt.