Filter piston apparatus for dispensing pulverulent bulk material

A filter piston apparatus that dispenses predetermined volumes of pulverulent bulk material has a metering chamber which accommodates in each case a predetermined volume of bulk material, which is present at the end of a circular-cylindrical bore and which has its base formed by a filter of the piston. The metering chamber is attached to a positive-pressure or negative-pressure gas source through the filter, which is permeable to gas but impermeable to the bulk material. A piston wall has a transverse slot and an inner groove located radially opposite the transverse slot, such that the filter can be pushed into the slot from the outside and, when seated in the piston, can be secured on both sides in the axial direction of the piston along it periphery.