Apparatus for introducing an agent into a liquid or gas at a controlled rate

An apparatus for introducing an agent into a liquid or gas at a controlled rate, where the agent is miscible with such liquid or gas, said apparatus comprising:

• (a) a reservoir for storing said liquid or gas, said reservoir being divided into a plurality of small units connected in series;
• (b) an inlet means for supplying said liquid or gas to said reservoir;
• (c) an outlet means for discharging said liquid or gas from said reservoir, said inlet means and said outlet means being located at opposite ends of each of said units of said series;
• (d) a filter element containing granular activated carbon located in each unit of said reservoir adjacent to said outlet means;
• and
• (e) at least one agent dispenser located within said reservoir adjacent to said inlet means and surrounded by said liquid or gas, said dispenser containing said agent, and said dispenser being constructed of a hollow casing of polystyrene having a co-efficient of cubical expansion that differs from the co-efficient of cubical expansion of said liquid or gas, said dispenser having at least one opening for permitting the flow of said liquid or gas between said hollow casing and said reservoir;
• wherein said agent is introduced into said liquid or gas surrounding said agent dispenser through said liquid or gas being drawn into and expelled from said dispenser through said at least one opening due to variations in the internal pressure of said dispenser resulting from thermal expansion and contraction of the dispenser and its contents due to variations in the temperature of said liquid or gas surrounding said dispenser.