The inlet line to the pressure chamber contains a 0 to 3000 pound pressure gauge and a safety diaphragm. The cone shaped top closure is o-ring sealed and designed to open or close using only hand turning. The exhaust needle valve is positioned behind the pressure chamber so that it is warmed by the water used to raise the chamber through the critical temperature. The arrangement prevents the exhaust valve from frosting during venting. The stainless steel beaker is provided for immersing the pressure chamber and vent valve in warm or cold water.
Surface tension becomes zero, and the boundary between liquid and gas vanishes.
It is usually necessary to start by replacing the water in the specimens with a fluid miscible with a liquefied gas. Many specimens can be treated in a short time. The transitional fluid must have a critical temperature higher than room temperature, but low enough so that the temperature at the critical point will not damage biological specimens. Freon 13 can be used with ethyl alcohol as the dehydrating fluid and Freon TF as the Intermediate fluid. Nitrous oxide can be employed directly with wet specimens.