Date: Fri, 15 Nov 1996 14:09:10 +1000
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From: Kim Baublys <[log in to unmask]>
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Subject: del 34S analysis of hydrogen sulfide
I am seeking information on two matters.
The first is Re: del 13C analysis of carbonate samples containing pyrrhotite.
I am interested in finding out how people scrub hydrogen sulfide gas from
samples. The gas comes from pyrrhotite contamination in the carbonate which
hydrogen sulfide when reacted with orthophosphoric acid. Lead acetate has
The second matter is Re: del 34S analysis of hydrogen sulfide gas.
Has anyone done analyses of this type and does anyone have any suggestions
regards conversion of hydrogen sulfide to the sulfate or the sulfide?
Any suggestions on procedure or pihers to get would be appreciated.
Stable Isotope Geochemistry Laboratory
Department of Earth Sciences
University of Queensland 4072
Elimination of H2S gas derived from sulphide contamination of carbonate
samples is easy. Among the several methods available, we use an Ag3PO4 trap.
We put about 1-2 gr of the silver phosphate in a valved glass container,
that we connect to one of the collection ports of our vacuum line. Since
silver phosphate, as most silver compounds, is light sensitive, you have
to take the precaution of keeping it in the dark until used.
Carbonate reaction proceeds as usual. After cleaning of the water, ...etc,
we justs freeze the CO2 + H S mixture into the silver phosphate trap,
allow to thaw and maintain it like that for about five min. The H2S reacts
with the silver phosphate to produce Ag2S, thereby efficiently eliminating
any sulphur contamination from the CO2. Afterwards, proceed as normal.
Should you decide to use this method, remember to store the Ag3PO4 in the
dark. The stuff is pretty expensive, and it will degrade very fast when hit
Regarding the analysis of the pyrrhotih paper by Canfield et al (1986). You can
attack the sample with HCl in a nitrogen atmosphere, collect the evolved
H2S in a zinc acetate + ammonia trap and convert the sulphur acetate to
Ag2S using AgNO3 0.1 M. The method is quite well described in the paper
mentioned, but if you have further questions, contac me again. We have some
experience with it.
Stable Isotope Lab.
Canfield, Raiswell, Westrich, Reaves and Berner (1986) "the use of
chromium reduction in the analysis of reduced inorganic sulfur in sediments
and shales". Chem. Geol., 54, 149-155.
Hall, Pelchat and Loop (1988) "separation and recovery of various sulphur
species in sedimentary rocks for stable sulphur isotopic determination".
Chem. Geol., 67,