Pneumatic trough

A pneumatic trough is a piece of laboratory apparatus used for collecting gases, such as hydrogen, oxygen and nitrogen.

[1] Four items are required for gas collection with a pneumatic trough:[2] Pneumatic troughs require a liquid such as water.

Scientists also have used mercury in pneumatic troughs, but usually only for the collection of water-soluble gases.

Health and safety issues surrounding mercury generally prohibit its use in modern-day pneumatic troughs.

The outlet tube from the gas-generating apparatus is inserted into the opening of the bottle so that gas can bubble up through it, displacing the water within.

Pneumatic trough with bulb suspended from hanger, as invented by Stephen Hales
Pneumatic trough, and other equipment, used by Joseph Priestley