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DESCRIPTION
SPEX SamplePrep Freezer/Mills are cryogenic laboratory mills
that cool samples to cryogenic temperatures and pulverize them
by magnetically shuttling a steel impactor back and forth against
two stationary end plugs. Since the vial is closed, the integrity of
its contents is maintained: hazardous or critical samples are easily
controlled, cleanup is simplified, and cross-sample contamination
is eliminated. Because the vial is immersed in liquid nitrogen
throughout the grinding cycle, the sample is kept at cryogenic
temperatures and its key aspects preserved. These features have made
SPEX SamplePrep Freezer/Mills the most effective in the world. They are the “mills of last
resort” for many normally ungrindable samples, or samples whose composition is altered by the
heat generated by conventional grinding.
NOTE: Before operating the 6750 Freezer/Mill, familiarize yourself with these instructions. The
Freezer/Mill is different in its principles and operation from any other laboratory mill. If you’re
familiar with the mill and want to proceed directly to grinding, the “Running the 6750” section
on p. 16 can serve as a general review of the actual operation of the mill.
We suggest unpacking the mill, then going over its various features with these instructions in
hand before attempting to add liquid nitrogen or grind a sample.
VERY IMPORTANT: Liquid nitrogen not only embrittles samples through severe chilling,
making them “grindable,” but also cools the magnetic coil which powers the 6750 Freezer/Mill.
If the mill is operated without liquid nitrogen for a period of about one minute, the coil will
become very hot and may sustain permanent damage. This 6750 Freezer/Mill has a liquid
nitrogen sensor that shuts down the mill when the temperature in the “tub” rises to the point
where the coil is at risk. Nevertheless the nitrogen level should be visually checked during
extended runs as well as before every run. The Freezer/Mill warranty does not cover damage to
the coil caused by operating the mill with little or no liquid nitrogen.
SAFETY NOTES:
1) Liquid Nitrogen can be hazardous. Its boiling point is -195.8
o
C. When working with liquid
nitrogen directly or indirectly, you must wear cryogenic gloves to protect your hands. Be careful
not to splash liquid nitrogen on clothes or unprotected skin. Always use cryogenic gloves when
handling very cold objects or materials: sample vials, the nitrogen tank valve or hose, chilled
Freezer/Mill components, etc. We also recommend safety goggles to protect your eyes.
2) Do not attempt to operate the 6750 Freezer/Mill without liquid nitrogen
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