Liquid CO2 Visualization Apparatus


The apparatus described here is a teaching tool for instructors to illustrate to students the effect that pressure, temperature and volume have on states of matter (i.e. solid, liquid, gas).

Carbon Dioxide is a gas at room temperature and pressure, although most everyone is familiar with solid CO--dry ice--which has a temperature of -109.3°F at atmospheric pressure and slowly sublimes. CO2 can be stored as a liquid at room temperature under high pressure, as is done in fire extinguishers and soda carbonation fountains. However, these cylinders are made of metal to store the CO2 safely under such high pressures and one cannot see the liquid.

The apparatus described here allows people to see all three phases of CO2 at ambient temperatures.  While the apparatus has multiple safety features, it can briefly be described as a polycarbonate tube fitted with a pressure gague manifold.  As the dry ice warms slowly in the tube, the observers can watch the pressure increase on the gague.  Just slightly below 100 psi, the dry ice begins to melt and one can see the CO2 both melting and boiling. Eventually all of the dry ice melts to form the liquid CO2.  The pressure can be released manually with an open/close valve, and when it is opened, the observers get a very cool illustration of the relationship between pressure, temperature, and volume (no spoilers here!).

This apparatus could make a useful demonstration at many age levels, from elementary school through college.

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Patent Information:
For Information, Contact:
Christine Gramer
Senior Technology Development Associate
University of Oregon
David (Randy) Sullivan
Lallie McKenzie