A preferably pulverulent formulation to be dosed is received in a dosing chamber having a partly gas-permeable wall. The introduction and discharge of the formulation is achieved by means of a pumping device that alternately generates a negative pressure and an excess pressure in the dosing chamber. The dosing chamber can also be displaced between a receiving position and a discharge position by means of a piston, the piston controlling the negative and excess pressure in the dosing chamber. Furthermore, the size of the dosing chamber is adjustable.
