Sean Ragan followed a 19th century design by Petrus Jacobus Kipp to create this benchtop gas generator. He writes:
If you should find yourself in need of small volumes of gas at about atmospheric pressure for a reaction or project, generating it on the bench can be a convenient and inexpensive alternative to buying or renting a gas cylinder. It turns out there are a number of useful gas-generating reactions between solid- and liquid-phase reagents. Kipp’s design incorporates the clever feature that stopping the flow of gas separates the liquid and solid reagents inside the instrument and thereby stops the reaction. Thus the generator only produces gas when you need it, and may remain in a stable equilibrium state on the bench for days at a time, ready to resume operation as soon as you open the valve.
Illustrated Guide to Home Chemistry Experiments by Robert Bruce Thompson