after purification flowing out via the perforations 320 while the perforations 321 function as overflows especially when the deluge in the column has been actuated the cables 221 and 222 are cables for retaining the upper part 229 should the bolts 330 rupture due to the pressure of the resin on the plate 305 the bottom of the cylinders 217 218 is fixed to the body 201 of the column at 331 and 332 respectively the operation of the device according to the invention and in particular the system for maintaining pressure on the resin in the column will now be explained below the resin balls are kept at the top of the column by a filter equipped with two seals u2014 one of the scraper type and one of the o ring type this system provides good sealing so as to prevent the entrainment of resin balls out of the column in order to improve the effectiveness of the purification it is important to work with a compacted bed to do this the top of the column is composed of a piston equipped with the filter described above and with two cylinders responsible for applying a constant holding force on the resin bed these cylinders are preferably of the pneumatic type the holding force being set by the pressure of the compressed air supplied to the cylinder preferably for safety reasons the cylinders are connected to the piston via rupture bolts so as to allow the piston to be completely disengaged in the event of decomposition of the hydrogen peroxide the bottom of each column is equipped with a liquid distributing device so that the liquid is distributed.