Abstract: A method and an apparatus is proposed for volumetric dosing of a predetermined or selected dose of a product in the form of powdery material, a slurry, or a suspension (16) from a multiplicity of supply sources (18), using a multiplicity of dosing chambers (5), wherein at least one dosing chamber (5) is allocated to and in fluid communication with each supply source (18), and wherein one wall segment of each dosing chamber (5) is formed by a diaphragm (4), comprising the steps of selecting a desired supply source (18), displacing a diaphragm (4) from an initial position (8) providing a maximized volume of the dosing chamber (5) allocated to the selected supply source (18) towards a final position (17) in which the volume of the dosing chamber (5) is minimized, and thereby discharging the product (16) through an output (26), and refilling the dosing chamber (5) with product (16) from the respective supply source (18), thereby returning the diaphragm (4) into its initial position (8).