Critical Point Drying Procedure
Item needed to be complete for Critical Point Drying.
For step 5 of Critical Point Drying procedure:
- Fill green ice bucket from cabinet to left of the Critical Point Dryer with ice from room 248.
- Using the 5000ml pitcher from the top shelf in the prep room, mix ice with cold tap water to bring temperature of water between 15°C
Critical Point Drying
- Open the drying chamber by turning front locking screw (1) counter-clockwise then turn
the yoke (2) clockwise until it stops. Pull up on the yolk (2) until is disengages (this is airtight
and takes gentle pressure).
- Place your prepared specimen in the mesh basket (6) or one of the stainless steel small specimen holders and place in the DCP-1 body.
- Check the neoprene gasket (4) and the O-Ring (5) for damage and proper fit.
- Tighten the front locking screw (1) and turning it clockwise until tight.
- Immerse the chamber in the metal beaker fill the beaker with the 15° to 25° C water from Step A. The water should come over the left hand
U-shaped fitting but not to where the YOLK (2) ASSEMBLY and BODY (7) meet. Pivot the swivel shelf under the beaker to hold.
- Open the CO2 tank valve.
- Open chamber inlet valve to introduce liquid CO2 into the drying chamber.
- Slightly open the chamber exhaust valve (rear hand screw) to allow a small even flow of CO2 to flush the chamber. The Pressure gauge will
show about 900 pounds pressure in the chamber.
- Continue to bleed off CO2 (you may need to open the chamber exhaust valve periodically) until the amyl acetate odor is undetectable.
Then close exhaust valve (rear hand screw) and close the CHAMBER INLET VALVE.
- Pour out the cold water from the beaker and rinse under hot tap water until the beaker is warm to the touch. Replace the beaker onto the swivel
shelf and fill the BEAKER with 50° C water until the water comes over the left hand U-shaped fitting but not to where the YOLK (2) ASSEMBLY and
BODY (7) meet.
- The chamber will warm and the pressure will rise to about 1650 psi. During this rise it will pass through the critical point at about
- Vent the chamber slowly by lightly opening the CHAMBER EXHAUST VALVE; venting
should take between 5 to 10 minutes.
- Remove the metal BEAKER and dry outside of the chamber assembly carefully (you don’t want to re-introduce moisture to the sample).
- Loosen the front LOCKING SCREW until the top assembly is loose and the YOKE can be turned counter-clockwise. Some water will be under the
YOKE so carefully dry this off before lifting off the top.
- Remove your specimen and check the neoprene gasket (4) and the O-Ring (5) for dirt before replacing.
- Close the CO2 tank valve.