Dear Patrick,
Although the earlier reactions in general were very positive according
to longer storage of hydrogen gas in glass - both sealed capsules and
stop-cock closed ones, I like to bring forward some references.
One about hydrogen glass exchange:
The well known paper by:
M.L. Coleman, T.J. Shepherd, J.J. Durham, J.E. Rouse and G.R. Moore,
Reduction of water with zinc for hydrogen isotope analysis. Anal. Chem.
54, 993-995, 1982, and two others:
C. Kendall and T.B. Coplen, Multisample conversion of water to hydrogen
by zinc for stable isotope determination. Anal. Chem. 57, 1437-1440,
1985 and
J.V. Turner and V. Gailitis, Single-step method for hydrogen isotope
ratio measurement of water in porous media. Anal. Chem. 60, 1244-1246,
1988.
Another is about hydrogen fractionation by the zinc method:
A. Demény, H isotope fractionation due to hydrogen-zinc reactions and
its implications on D/H analysis of water samples., Chem. Geol. 121,
19-25, 1995.
My own experience with stopcock (glass core Lauwes-Hapert type, with
Apiezon greased viton o-rings) closed pyrex tubes storage of hydrogen
gas, collected on active carbon grains, is fractionation in rather short
time during storage - even overnight measurable fractionation occurs.
H-gas probably diffuses through/along the greased o-ring if not
exchanging with H-gas in the pyrex???. Of course, the active carbon
containing tubes never are opened to air and are "burned-clean" on a
vacuum line regularly. Personally, I have no experience with H-gas in
fusion-sealed containers (if there is a possibility to do that without
storing the zinc/zincoxide too).
All the papers by Coleman et al., Kendall & Coplen, and Turner &
Gailitis, report fractionations of hydrogen with glass, and I am curious
about the difference in experience between these studies and the
reactions on the isogeochem list to have no exchange at all for long
time periods!!!!
Another factor, which may cause fractionation is the absorption of
hydrogen gas on the zinc/zinc-oxide material: see for this the Demény
ref., although not related to this glass-exchange problem it may be
mis-interpreted to be the glass causing this fractionation. This is - if
remembered well - easily cured by heating the zinc/zincoxide to release
the hydrogen gas. Certainly Atilla Demény can comment this if I
remembered wrongly.
I like to see the others reactions on this matter.
Pier de Groot.
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Dr. P.A. de Groot
University of the Witwatersrand
Economic Geology Research Unit
Department of Geology
Private Bag 3
2050 Johannesburg
South Africa
Tel. +27 11 7162564
Fax. +27 11 3391697
E-mail <[log in to unmask]>
Visit the combined HOME-PAGE of EGRU-Geology on the Internet:
http://www.wits.ac.za/science/geology/1stpage.htm
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