An apparatus containable entirely within the tank of a toilet tank and bowl combination and adapted to dispense a predetermined amount of a liquid formulation into the toilet bowl in response to cycling of the water level in the tank during a flushing operation of the toilet. The apparatus comprises a reservoir for storage of a supply of the liquid formulation and a positive displacement dispensing pump which is driven through its working stroke by a float vertically movable in response to the cycling water level in the tank, said float having an open top and sealed bottom and peripheral sidewall defining a vertically extending interior cavity which nests the reservoir.