Dachun,

See the paper by Rye, Bethke, and Wasserman 1989 USGS Open file report 89-5
for details of the extraction and systematics.  In my experience, hypogene
alunites are pretty clean and easy to extract the OH, but supergene
alunites can be very difficult.  Best results are obtained by very slow
heating; if any liquid droplets (sulfuric acid) form in the system at all,
the sample will be no good, and the line will require thorough cleaning
before another analysis.  I found some alunites from which I could NEVER
get good results.  H isotope values will always be lower than reality when
you form sulfuric acid, presumably because the acid sequesters the D making
whatever water gets through the system lower.

cheers,
greg

At 11:22 AM 11/12/1997 -0800, you wrote:
>     Dear All: I will be very grateful if somebody can give me suggestions
>or references as  how to extract water from alunite,
>K2SO4.Al2(SO4)3.4Al(OH)3, for D/H and 18O/16O  analysis. I tried vacuum
>distillation at 550 degree C. Instead of pure water, I  got sulfuric acid
>with very strong smell of SO2. Best regards. Dachun Zhang Global
>Geochemistry Corp. 6919 Eton Ave. Canoga Park, CA 91303
Dr. Greg B. Arehart
Department of Geological Sciences
University of Nevada - Reno
Reno, NV  89557-0132  USA
ph: 702-784-6470
fax: 702-784-1833
email: [log in to unmask]