Stable Isotope Geochemistry


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"Craig H. Moore" <[log in to unmask]>
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Stable Isotope Geochemistry <[log in to unmask]>
Wed, 27 Jul 2005 09:17:33 -0500
text/plain (149 lines)

We have been using BrF5 in our oxygen line for over 20 years.  We have a 
U-shaped waste trap that we empty after every 50 to 60 samples are run 
or if no one will be available to keep liquid nitrogen on the trap .  We 
keep the trap frozen with liquid nitrogen during removal and have a 
second trap that we put on the line as soon as we remove the first.  
Then we take the frozen trap to the roof of the building (still in 
liquid nitrogen), invert it on a stand that has a hook to hang it on, 
stand back (and upwind), and let it thaw.  The residue will slowly drip 
out of the tube onto a thick piece of high-density plastic where it 
evaporates.  The process takes anywhere from 15 minutes to over an hour, 
depending on the temperature outside.  In years past the University had 
a cement pad in a remote area where we basically did the same thing.  
Because the BrF5 is always frozen when someone is near it, protective 
equipment is not needed.  Our chemical and environmental safety officer 
believes this is a better method than emptying it under a hood.


Craig H. Moore, Ph.D.
Department of Geological Sciences
Indiana University
1001 East 10th Street
Bloomington, IN 47405

Julia Cox wrote:

> Hi Kim,
> I have another question for you, since you were so helpful earlier.  
> How do you dispose of excess BrF5 and residue from your line?  You've 
> stated you remove your coldfinger trap daily.  Do you react the 
> residue with something?  Do you store it for disposal in larger 
> quantities?  Also, what type of personal protective equip. do you use 
> when handling the waste?
> I have been told to collect waste BrF5 on the line for several days 
> and then basically pour it out over a bucket of limestone chips (in a 
> fume hood).  I'm hoping there's a better way than that.
> Thanks for your advice,
> Julie
> Kim Baublys wrote:
>> Hi Julie,
>> I have been using BrF5 in our manual extraction line for many years 
>> and we
>> have found that keeping things simple gives the best results.  We 
>> actually
>> found that the Hg diffusion pump was causing vacuum problems (lots of
>> grunge after many years of operation).  So then I changed to a 
>> silicon oil
>> diffusion pump but it didn't appear to make any difference to the 
>> ultimate
>> vacuum.
>> As a result I now run with a large liquid nitrogen trap just in front of
>> the rotary pump  plus another liquid nitrogen trap further up the 
>> line in
>> addition to the standard traps.  This system has been working very 
>> well for
>> the past year.  I just make sure that I freeze the residues from all 
>> traps
>> into the upper cold finger before daily disposal.  This minimizes any
>> rubbish going into the rotary pump.  My advice would be not to use 
>> the soda
>> lime at all. It will cause too many problems over time and as you have
>> found out it takes too long to pump down.  My current system takes 
>> only a
>> few minutes to recover between samples.   I am hoping that if I 
>> change the
>> rotary pump oil regularly that I should have many trouble free years of
>> operation.  Or until I have to source another cylinder of BrF5. :)
>> Cheers
>> Kim
>> Kim Baublys
>> Stable Isotope Laboratories
>> Department Of Earth Sciences
>> University of Queensland 4072
>> Australia
>> Ph:   +61 7 3365 1131
>> Fax: +61 7 3365 1277
>> At 05:39 PM 5/07/2005 -0400, you wrote:
>>> BrF5 users:
>>> We have 2 vacuum lines that see bromine pentafluoride - a laser
>>> fluorination line plus a line used to distill and load BrF5 into a 
>>> Kel-F
>>> container.  The fluorination line has Hg diffusion pumps for trapping
>>> residual BrF5 and protecting the mechanical pump downstream.  On the
>>> distillation line we were planning to use an in-line trap filled with
>>> granular soda lime.   However, I have been questioning how well the 
>>> soda
>>> lime will work.  When we first put the trap in place, we could not pump
>>> the line down.  After taking the trap out and looking at the 60 micron
>>> filter on the downstream side, we saw the filter was at least partially
>>> clogged with tiny purple crystals.  Fluorite?  If so, that is 
>>> surprising
>>> since the line had seen very little BrF5 so far.  After re-installing
>>> with a clean filter, we observe that the line is pumping down, but very
>>> slowly.  The soda lime is taking days (almost a week now) to degas.
>>> I'm interested in recommendations you have for protecting vac pumps 
>>> from
>>> BrF5, and whether using soda lime is a practical solution.
>>> Thanks for any suggestions!
>>> Julie
>>> -- 
>>> Julia Cox
>>> Dept. of Geology
>>> University of Georgia
>>> Athens, GA  30602
>>> 706-542-1005
>> Kim Baublys
>> Stable Isotope Laboratories
>> Department Of Earth Sciences
>> University of Queensland 4072
>> Australia
>> Ph:   +61 7 3365 1131
>> Fax: +61 7 3365 1277