Critical
Point Drier

EMS 850 Critical Point Drier
What is CRITICAL POINT DRYING?
Critical Point Drying is so named as it includes, as part of its process, the occurrence known as the continuity of state for which there is no apparent difference between the liquid and gas state of a medium, the surface tension between this interface reducing to zero. This occurs at a specific temperature and pressure with resulting density, and is known as the Critical Point. This condition of zero surface tension can be used to dry Biological Specimens, avoiding the damaging effects of surface tension.
In biological specimens we are mainly concerned
with the removal of water. Unfortunately, the critical point for water
of +374°C and 3212 p.s.i. is inconvenient, and would cause heat damage
to the specimen. The most common and convenient transitional medium for
critical point drying is Carbon Dioxide (CO2), which has a
critical point at 31°C and 1072 p.s.i. However, it is not miscible
with water, and therefore, we have to involve a third medium, commonly
Acetone, which is termed the intermediate fluid. We can now convert our
transitional fluid, typically CO2, from liquid to gas without
surface tension at the critical point.
The EMS 850 Critical Point Drier is designed for use with CO2, having first replaced any water in the specimen by a series of dehydration, often in the same fluid such as Acetone, which will also be the intermediate fluid.
(Wet Specimen)WaterAcetone30%100%CO2 C.P.D.(Dry Specimen)
The specimens for critical point drying are located in the pressure
chamber of the EMS 850. The chamber is pre-cooled to allow it to be readily
filled with liquid CO2 from a gas cylinder. The chamber is then heated
to just above the critical temperature with subsequent critical pressure
being achieved. The CO2 gas is vented through a needle valve,
to avoid specimen distortion.
The EMS 850 is fitted with thermoelectronic Heating and Cooling and Temperature control of +5°C on Cooling, and +35°C on Heating. This ensures the critical point is accurately obtained, avoiding excess pressures or temperatures, or the need to rely on pressure relief valves to control pressure during the heating cycle. The chamber is vertical, with top loading, to ensure specimens do not become uncovered during the drying process, with a side viewing port to locate the miniscus for the correct level when initially filling the chamber.
Note: The EMS 850 is now fitted with a fine let down needle as standard and flow gauge is not required.
Features
- Vertical chamber with top filling and bottom draining
- Normal operating temperature 35°C pressure 1500 psi
- Thermoelectric Peltier cooling and heating
- Fine control needle valve pressure letdown
- Illuminated chamber with side viewing port and protective 'Lexan' shield
- Stirrer system for enhanced solvent exchange
- Temperature monitoring and control with thermal cut-out protection
- Pressure monitoring with pressure relief valve and rupture disc protection
- Polycarbonate safety shield
Specifications
| Instrument Case | 450mm(W)x350mm(D)x175mm(H) |
| Weight | 12Kg |
| Specimen Chamber | 30mm(Dia.)x40mm(H)(Tested to 3000 psi) |
| Temperature Gauge | 0-120°C |
| Thermal Cut-Out | 40°C |
| Pressure Gauge | 0-3000 psi |
| Pressure Relief | At 1500 psi |
| Rupture Disc | At 1900 psi |
| Peltier Cooling/Heating | +5°C to +35°C |
| Two On/Off Valves | Inlet/Outlet/Cool/Vent Needle Valve Letdown |
| Supply | 115 volts 60Hz (6 amp Max incl pump) 230 volts 50Hz (3 amp Max incl pump) |
| Services | Requires CO2 gas cylinder
direct |
Ordering Information
| 91090 | EMS 850 Critical Point Drier complete | POR | Request Quote |
Replacement Parts
| 91091 | Mesh Basket | $250.00 | Add to Cart |
| 91092 | Porous Spec Pots | $90.00/pack | Add to Cart |
For our Critical Point Drier Accessories
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Critical Point Drying Principles









