Abstract: A novel chemical dispenser for dispensing a predetermined volume of a chemical solution into a body of liquid, such as water in a toilet tank, in response to a change in the level of that liquid comprises (1) a container which holds the solid chemicals to be dispensed, (2) an air vent extending from the top of the container, (3) a siphon which enters the container at a point located below the top of the container and has a U-shaped bend extending above the top of the container but below the top of the air vent, and (4) a specially designed fluid communication means between the siphon and the container, which reduces or eliminates the possibility that any gas bubbles evolved by the solid chemical in the dispenser will become entrapped in the siphon and impede its normal operation.

Abstract: A novel chemical dispenser for dispensing a predetermined volume of a chemical solution into a body of liquid, such as water in a toilet tank, in response to a change in the level of the liquid comprises a container which holds the solid chemicals to be dispensed, an air vent extending from the top of the container, and a siphon which enters the container through a deck located below the top of the container and has a U-shaped bend extending above the top of the container but below the top of the air vent. The dispenser structure provides substantial isolation of the chemical solution in the dispenser from the surrounding tank water between flushes without the presence of any isolating air bubbles and also provides a color change signal indicating when the solid chemical within the dispenser is depleted.