Abstract: The apparatus according to the invention comprises a casing. The casing consists of two chambers: an inlet chamber and a filtering chamber each having a conical receptacle for collecting solid chlorides. The inlet chamber and the filtering chamber are provided each with guide webs and are separated from each other by a partition wall comprising a gas duct. The gas duct establishes a communication between the lower portions of the chambers in such a manner that the inlet end of the gas duct is arranged under the guide webs of the inlet chamber and the outlet end is arranged under the guide webs of the filtering chamber. The filtering chamber has inlet pipes for admission of pulp. A pipe for admission of a chloride pulp is arranged above the guide webs at a distance of from one to two times the diameter of the filtering chamber. The pipes for an oxychloride pulp is arranged below the guide webs which are permanently covered with a filtering material.