Mariotte's bottle

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Mariotte’s bottle is a device that provides a constant pressure that will deliver a constant rate of flow from closed bottles or tanks. It is named after French physicist Edme Mariotte (1620-1684).

The design was first reported by McCarthy (1934). As shown in the diagram, a stoppered reservoir is supplied with an air inlet and a siphon. The pressure at the bottom of the air inlet is always the same as atmospheric pressure; for if it was greater, air would not enter; and cannot be less as it is in contact with the atmosphere. If the entrance to the siphon is at the same depth, then it will always supply the water at atmospheric pressure and will deliver a flow under constant head h, regardless of the changing height of water within the reservoir.

This apparatus has many variations in design and has been used extensively when a constant water pressure is needed, e.g. supplying water at constant head for infiltrometer.

[edit] Reference

• McCarthy, E.L., 1934. Mariotte's Bottle. Science, 80:100.