The invention concerns the operation of a pneumatic device for the metered delivery of a liquid and a pneumatic device particularly suited for operation in accordance with the invention. The pneumatic device has a pressure tank that can be connected to a compressed air source by means of an inlet valve and with the surroundings by means of an outlet valve. For delivery of the liquid, a pressure pulse is applied to the liquid container containing the liquid in that the pressure tank is temporarily connected to the liquid container via a changeover valve. After the end of the pressure pulse, the pressure prevailing in the pressure tank is increased to a value that is greater than the set value to be achieved during the pressure pulse.