Abstract: A liquid dosing apparatus comprises a tank (8) to be repeatedly filled with liquid to an upper level; a float (24) adapted to rise in the tank concurrently with the filling thereof and, each time the upper level has been reached, to be wholly or partly filled with liquid so as to sink in the tank, thus actuating a draining siphon (15) which drains the tank to a lower level; and a float siphon (27) draining the float (24) so that this will float again when the liquid level rises after the tank has been drained. The actuating of the draining siphon (15) by the float (24) is achieved by the provision of a chamber (13) which communicates with the tank (8) so as to be filled with liquid when the tank (8) is being filled, an inlet (20) of the draining siphon (15) being connected to the chamber (13). The sinking movement of the float (24) reduces the amount of liquid in the chamber (13), the liquid being pressed into the inlet (20) of the draining siphon for actuating the latter.