Making KBr Pellets
For all KBr
using the Midvale-Heppenstall Press.
Users MUST read and understand operating
Do not use your own techniques to make KBr (Potassium Bromide) pellets follow the
instructions to obtain perfect pellets without damaging the expensive
press, die, or plunger.
Check the ANVIL the PLUNGER, and the base cleanliness. Please
take care and clean the die system after each use. Do
not wipe the polished faces with a cloth that has a hard abrasive
textures. Always use soft cloth or lens tissue.
We will try to polish out the imperfections made by careless
This KBr die is designed for pressing a mixture of potassium
bromide and your solid sample. A clean die will produce a thin
and transparent pellet about 13 mm in diameter.
Your pellet is then ready for analysis by FTIR. But remember you
must clean all materials and leave the press and die ready for
use by the next person. Please remember to clean your work area
and properly label all materials.
All users must first use the log
book to sign in according to the protocol given in the book, e.g.
your name, your professors name, the date of use, number of pellets
made, and any comment on problems or on the quality of the pellets
Making KBr Pellets
The following instructions require a press
and a standard die for making KBr pellets.
1. Place a few mg (not more than 300 mg) of
dry IR-grade KBr in an agate mortar. An amount of KBr sufficient
to cover an area of about 20 mm2 to a depth of 1 mm
2. Grind the KBr in the mortar until there is no evidence of crystallinity. A normal lab mortar will produce contamination of the pellet. An agate mortar avoids contamination.
3. Add a very small quantity of sample, about 1 to 2 mg is sufficient
or about about 1 to 2% sample to KBr ratio.
4.Grind the sample into the KBr
until it is uniformly distributed throughout the KBr.
photo by permission of International Crystal Laboratories, copyright ©2000-2010
5.Transfer some of the ground mix to the pellet making die and
make a pellet. Tamp the KBr powder/sample mixture down on the
anvil with the plunger of the die set.
6. Apply a small pressure to the die before pulling a vacuum.
Pull a vacuum for 1 to 2 minutes and continue the vacuum while
you apply full 10,000 pounds to 16,000 pounds of pressure pressure
to the die for 2 minutes.
7. Release the vacuum
first and then release the pressure
the die set. Remove the base by twisting it off and releasing
the 'O' ring seal.
9. Push the pellet out using
the plunger of the die set. Frequently the anvils will be lodged
in the barrel. Set the die set on transparent cylindrical pellet
extractor and either push with the press or by hand to extract
the KBr pellet. It is preferable to discharge the pellet
with the clear cylindrical pellet extractor located above the
end of the bore and
located beneath the assembly.
10. Design each experiment with properly labeled storage containers for each pellet. Always prepare a blank KBr pellet.
the FTIR spectrum of the KBr-sample pellet.
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