Thermodynamics ** 4C33.50 ** Change of state

Vapor pressure

Pulse glass

WARNING: The liquid in the pulse glass has a low boiling point. Body heat, from your hand, is all that is necessary to make it boil. No hotter heat source should be used.


Theory: The volatile liquid is sealed in the pulse glass under reduced pressure, so the pressure comes from vapor pressure of the liquid. Heating one bulb with your hand increases the vapor pressure in that bulb, forcing the liquid through the connecting tube into the other bulb in a series of pulses.

Description: Enclose one bulb of the pulse glass with one hand. It generally works best if you hold the bulb with the pointed top, and angle the pulse glass slightly so all the liquid starts off in the bulb you're holding. After several seconds the liquid should move to the other bulb, and then will bubble quite violently for a few seconds.

Setup time: 1 minute

References: (available in the demo room)