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10 • General Information on Freeze Drying
b) ice condenser with temperatures from -50°C to
-105°C (depending on type of unit) to remove the
water vapour from the chamber
(= vapour pump)
Sublimation
The principle of sublimation is briefly explained using the phase
diagram of water (freeze drying of mainly aqueous solutions, see
vapour pressure curve). If the atmospheric pressure is higher than
6.11 mbar, water passes through all three phases (solid, liquid, gas)
when the temperature is lowered or raised. At 6.11 mbar the melting
pressure curve, vapour pressure curve and sublimation pressure
curve meet in one point called triple point. At this point all three
phases occur in parallel (simultaneously). Below this point, i.e. the
pressure is lower than 6.11 mbar, the ice is converted directly from a
solid to a gaseous phase on reaching the sublimation pressure curve
(vapour pressure curve above ice).
Operating Manual Freeze Dryer ALPHA 1-2 LDplus
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