Eudiometer

Eudiometer, a glass vessel, largely used in gas analysis. Various forms of eudiometers exist, many specially adapted for some particular analysis. The most common form consists of a straight tube of thick glass open below and closed above, upon which is accurately engraved a scale, generally in millimetres. Through the glass near the top are sealed two platinum wires across which an electric speerk can be passed. The mode of use consists in placing a known quantity of gas into the eudiometer over mercury, then adding an amount of oxygen (other gas if necessary) and exploding.

From the diminution in volume (and further diminution by action of different absorbents if necessary) the quantity of hydrogen or other detonating gas is known.