Archive for critical opalescence

Critical Opalescence in Carbon Dioxide

Posted in The Universe and Stuff with tags on January 28, 2016 by telescoper

Fascinating demonstration of critical opalescence..

Protons for Breakfast Blog

One feature of the teaching at Dalhousie University’s Physics Department is a laudable emphasis on demonstrations.

Visiting Professor Tom Duck there, I was delighted to be shown a demonstration I had heard of, but never seen: the phenomenon of critical opalescence in carbon dioxide.

I have written about critical opalescence previously on this blog (here) and with more pictures (here), so I won’t repeat most of that.

In my previous articles I described the phenomenon in two immiscible liquids which is an exact analogy for the physics of critical opalescence in a pure substance. But it’s not what physics students read about in text books.

Michael: What are you going on about?

The phenomenon occurs when one heats a liquid in a container with a small amount of free space.

  • As the liquid heats up, it expands causing its density to fall.
  • The liquid also evaporates causing the vapour (gas) pressure to…

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