Labconco FreeZone Plus 4.5 Liter and FreeZone -105 C Cascade Freeze Dry Systems 73870 Series - Manual (Page 8)

Chapter 1: Introduction
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If there is a problem with a particular type of sample melting when placed on the
freeze dry system, dilution of the sample with more water or providing some
insulation around the flask to decrease the rate of heat absorption by the sample
may help. If the eutectic temperature of the sample is –40 to –60°C, the freeze dry
system selected for use must be equipped with cascade type refrigeration so that
the collector temperature can be cooled to below –75°C, or a dry ice/solvent trap
may be used between the collector and the vacuum pump.
Samples Containing Volatile Substances
In certain cases the solvent in a sample to be freeze dried may contain volatile
components such as acetonitrile, methanol, acetic acid, formic acid or pyridine. In
addition to these substances having an effect on the eutectic temperature, they may
increase the vapor pressure at the surface of the sample. Also, compared to water,
they will require the absorption of less heat for sublimation to occur. Hence,
samples that contain volatile substances will have a greater tendency to melt,
particularly when placed in flasks or exposed to room temperature. If a sample
containing a volatile substance tends to melt when placed on a freeze dry system,
dilution of the sample with more water will help keep the sample frozen. For
example, a 0.2M solution of acetic acid is much easier to freeze dry than a 0.5M
solution.
Safety Symbols
Your freeze dry system was designed with safety in mind, however conditions may
exist that could be hazardous.