FRITSCH PULVERISETTE 2 - Manual (Page 30)

NOTICE!
If liquid nitrogen is added to the grinding process, it is only
possible when using the stainless steel grinding set (order
no. 462140.00) because the mortar is manufactured from
solid material (monolithic). All other grinding sets have a
plastic casing, which would be destroyed by adding liquid
nitrogen.
The grinding set must be cooled down with liquid nitrogen
outside of the PULVERISETTE 2 beforehand. This helps pre-
vent nitrogen from boiling inside the device.
CAUTION!
Wear safety goggles and suitable safety gloves when using
liquid nitrogen!
For this application, the grinding set is at room temperature, and only
the grinding stock has been pre-cooled. It is possible to use grinding sets
made of tungsten carbide, stainless steel, zirconium oxide or sintered
corundum, because the grinding set is not directly cooled.
For very temperature-sensitive grinding stock or material which is not
brittle, we recommend additional cooling with liquid nitrogen. This can
be added to the grinding stock in the mortar made of stainless steel
directly by filling it into the lid opening in the view window of the mortar
mill.
NOTICE!
To avoid damaging the plexiglas cover, we recommend
inserting a plastic or steel funnel into the lid opening and
using it to fill the nitrogen.
For a grinding duration of 5 min., 2 to 3 l liquid nitrogen are required.
This is added gradually via the opening in the lid. The sample is con-
stantly immersed in the circulating liquid nitrogen (N
2
) during the
grinding process.
We recommend not exceeding a maximum grinding duration of 10 to
15 minutes because the cooling effect is transmitted to the bearings and
the drives, causing the bearing grease to harden and the pestle to
become blocked, for instance. Likewise, the grinding parts should be
taken out of the device after grinding so that the bearings can cool back
down to ambient temperature. Remove developing water condensation
from the grinding chamber.
You can also use dry ice (solid carbon dioxide) for cooling. You should,
however, keep in mind that the surface of dry ice often contains frozen
condensate, which could potentially mix with your grinding stock causing
contamination.
Using the device
- 30 -