Martin Christ Alpha 2-4 LDplus User Manual
Page 16
16 General Information on Freeze-drying
Operating Manual Freeze Dryer ALPHA 1-4 LDplus / ALPHA 2-4 LDplus
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).
Conversion table "Vapor pressure above ice" (sublimation
curve)
Pressure units:
1mbar = 100Pa
1Pa = 0.01mbar
Temperature units:
273
t
T
273
T
t
32
8
.
1
t
t
F
8
.
1
32
F
t
t
T = thermodynamic temperature
K (Kelvin)
t = temperature in degree Celsius
°C
t
F
= temperature in degree Fahrenheit
°F