... is a standard laboratory apparatus for producing small quantities of any gas, through a chemical reaction between an acid and a solid material such as a metal.
It consists of three chambers, each roughly spherical, stacked one above the other. The solid material (e.g. iron sulphide) is placed in the middle chamber, and the acid in the top chamber. A tube extends from the top chamber, through the middle chamber, into the bottom chamber. The middle chamber has a tube with a stopcock attached, which is used to draw off the evolved gas. When the stopcock is closed, the pressure of the gas in the middle chamber rises and expels the acid back into the top chamber, until it is no longer in contact with the solid material, at which point the chemical reaction stops.
© Haydn Thompson 2017