Regarding my inquiry on the use of KBr to pasivate F2 in Fluorination lines:

I got a few answers to my request to my private e-mail address.
From the fact that I received more requests to pass on the results from this inquiry than answers to it I conclude that several people may be interested in this subject.
This is why I give a brief summary of the answers I received:

Design of KBr traps:
(1) U-shaped glass tubes with OD of approximately 1 cm and a total length of 30 cm are used.
Glass has the advantage that KBr can be seen.
Change in colour from initially white to yellowish tells you when it is time to replace or regenerate KBr.
In other labs three quater inch Ni tubing with a total length of 10 cm is used.
In this case one must rely on vacuum evolution to decide when it is time to replace the KBr.

(2)``hotter works better'' the trap should be heated to about 100oC


(3) KBr can be prevented from freely moving through the vacuum line on pumping by using either quartz wool plugs or, alternatively,  60 micron Ni fritted metal filters.

Pre-treatment of KBr
Apart from heating and evacuation there is no pre-treatment necessary.


Permeabilty of KBr
Generally a grain size equal or larger than 1 mm is recommended.
An alternative to the ordinary KBr reagent is broken infrared KBr window material.
This material shows excellent reactivity and permaebility at a temperature of 100oC and at a grain size of 1 to 2 mm.


That is it so far on the KBr business.
Any additional comments and hints from experienced users are very welcome!


Rainer


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Rainer Abart
Institut fuer Mineralogie-
Kristallographie und Petrologie
Karl-Franzens-Universitaet Graz
Universitaetsplatz 2
A-8010 Graz

Tel.: ++43-316-380 55 41
Fax:  ++43-316-380 98 65

e-mail: [log in to unmask]

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