Patent ID: 8166580

Claim:
Dispensing device for delivering a dose of a first liquid into a second liquid, the dispensing device comprising an enclosure and valve connected to the enclosure, and being operable such that, when the enclosure contains a first liquid, raising a level of a second liquid relative to the dispensing device so as to subject the enclosure and valve to hydrostatic pressure causes a dose of the first liquid to be displaced from the enclosure to establish a column of the first liquid that acts on the valve and thereby increase the potential energy of the valve, and subsequent lowering of the level of the second liquid relative to the dispensing device so as to reduce the hydrostatic pressure acting on the valve causes the valve to deliver the dose by release of the potential energy, wherein the dispensing device further comprises a vent chamber assembly comprising a vent chamber and first and second tubes, the vent chamber being connected to the enclosure by the first tube and to the valve by the second tube, the dispensing device being operable such that the column of the first liquid is established in the second tube, the vent chamber assembly being operable to vent displaced air from the dispensing device as the column of the first liquid is established, and the second tube being provided with capillary device operable to draw the first liquid along the second tube so as to accelerate the establishment of the column of the first liquid.