Abstract: An apparatus is disclosed for cleaning the bottom of mercury cathode electrolytic cells or the like, usable in closed cells which are cut off from the power supply and maintained under suction, characterized in that said apparatus consists essentially of a plate or strap that is displaceable along the bottom of the cell, and having an overall length substantially corresponding to the width of the cell-bottom to be cleaned, said strap normally resting on or near the bottom of the cell, and means for moving said strap along the bottom of the cell to scrape or dislodge mercury sludge and other residues that have accumulated during the operation of the cell. The means for moving the strap along the bottom of the cell may be manually actuated from outside the cell or they may be actuated by motor means situated outside the cell.