Pneumatic trough

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Pneumatic trough, as invented by Stephen Hales

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

Four items are required for gas collection with a pneumatic trough:

  • The trough itself, which is a large glass dish or a similar container
  • A gas bottle (or bulb), to hold the gas collected
  • A way to support the gas bottle or bulb, such as a Beehive shelf or a hanger (see picture)
  • A liquid in the trough

The bottle is filled with water, inverted, and placed into the pneumatic trough already containing water. 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.

See also[edit]

Pneumatic trough, and other equipment, used by Joseph Priestley

Further reading[edit]

  • Parascandola, John; Ihde, Aaron (1969). "History of the Pneumatic Trough". Isis. 60: 351–361. doi:10.1086/350503.