Abstract: The device comprises a syphon which connects a reservoir to a collecting recipient. The reservoir is supplied with liquid through a valve. A tube extends the reservoir upwardly and carries a detector which checks the level situated just above the syphon. A second detector is placed at the outlet of the syphon. The two detectors are electrically connected to the control of the valve so as to close the valve when the liquid reaches the detector checking the level and to preclude the opening of the valve so long as the detector receives liquid issuing from the syphon. The amount of liquid poured upon each opening of the valve is thus always strictly the same.Application to the preparation of mixtures having a precise and adjustable concentration, such as a mixture of powdered milk and water.