Abstract: The present invention relates to central reactor apparatus for applying cleaning treatments to plates such as regularly-shaped flat parts e.g. semiconductor media as used for making integrated circuits, or optical disks, etc. . . . The apparatus comprises a chamber including side walls, an end wall, an opening through a front plate facing said end wall, support means enabling a plurality of parts to be supported, means for injecting treatment fluids, closure means for closing said chamber, and discharge means for discharging said fluids, thereby enabling said parts to be treated by means of said fluids and subsequently enabling the chamber to be emptied. Said means for supporting the parts is secured to the closure means and is constituted by two side combs which are articulated on links enabling the combs to be tilted apart from each other to enable said parts to pass between them, and then to be tilted towards each other so that they engage beneath the parts and support them inside said chamber.