the invention relates to a method and equipment for quantitatively dosing small amounts of liquid , especially in clinical or other similar wet - chemical analyzers . the dosing employs a liquid space , the volume of which can be changed and which is connected to a dosing channel so that , by increasing or decreasing the volume of the liquid space , a suction or an injection through the dosing channel is achieved . the liquid space is formed by flexible bellows which are freely movable back and forth to provide the reversible deformations which change the volume of the liquid space . the movements are effected using an actuator which is connected to the bellows without transmissions containing sliding surfaces . the actuator comprises precisely repeatable positions and is calibrated according to the invention by measuring the sizes of the dosages produced by the movements between the positions . the dosing is effected after that by selectively repealing the calibrated movements . the actuator can be formed by a stepper motor , and a cam shaft rotated by the stepper motor propelling the bellows back and forth . the nonlinear interdependent relationship between the rotation of the shaft and the change in the volume of the liquid space makes possible a wide range of calibrated dosage sizes .