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Stable Isotope Geochemistry

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Subject:
From:
John Eiler <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Date:
Wed, 18 Feb 2004 13:30:34 -0800
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The next things I would check are:

1) the purity of your F2.  If it contains a non-condensible gas, its rate
of reaction will drop enormously at low pressures.  This will manifest
itself as a persistent trace residue of F2, despite initially vigorous
uptake (i.e., the first 99 % of reaction is rapid, but the last % takes
forever).

2) replace the metal of your NaCl/KCl trap.  You may have flourinated the
metal close enough to the down-stream end of your trap that it can now
slowly degas F2. Evidence in favor of this problem might include a trace F2
blank when the trap is hot but only O2 or innert gas is passed through it.

Good luck,

John


>Dear Isogeochemers,
>
>I am at wits end and need some help.  We are having terrible trouble
>neutralizing excess F2 gas from our fluorination line.  Originally, we were
>having wonderful success with NaCl.  Large amounts of F2 could be reacted
>to NaF + Cl2 in a matter of seconds.  Things were great for months.  Then,
>we replaced our used NaCl with a  new batach and the reaction no longer
>proceeds.  After replacing the NaCl, we may get it to work one time, but if
>we put in a new aliquot of F2, the rates of fluorination of the salt become
>painfully slow.  We have tried different temperatures of reaction, used KBr
>in place of NaCl and tried different grain sizes (melted the salts,
>etc.).  No matter what we do, the reaction of F2 with our salt is so slow
>as to be unusable.  I'm going crazy.  It used to work, but no longer.  I
>understand that the Earth's magnetic field is weakening, but I don't think
>that has anything to do with it!  We've even tried a different bottle of
>NaCl.  Still no success.  Any ideas would be appreciated.
>
>Sincerely,
>
>Zachary Sharp

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