Pressure Chamber for Demonstrating the Critical Temperature and Opalescence

This chamber with two transparent windows shows a gas and liquid mixture of Sulfur Hexaflouride. Hot steam is forced through pipes around the demo until the system reaches a critical temperature. When this occurs the meniscus in between the gas and liquid will disappear as everything in the chamber enters the same state of matter. Once the critical point is reached ice can be placed on the top to cool the whole system which results in the internal temperature dropping below the critical point. At this juncture the material in the chamber should undergo a process called optical opalescence where the size of the gas and liquid regions begin to fluctuate in size. This causes light passing through to undergo strong Rayleigh scattering and the chamber will appear cloudy until the temperature falls well below the critical point and there is again a region with liquid and a region with gas.