I am sorry but I was abroad and have just returned to Calgary. Unknown to
me, our server was replaced during my absence and I spent a few days
wondering what was the problem with my e-mail. I thank those who have
responded on my behalf. To summarize, oxygen isotopes can exchange between
quartz and SO2 but I think more rapidly between CO and quartz as shown in
the Sakai-Krouse paper. The Sakai-Krouse solution was to react the graphite
and BaSO4 mixture in a suspended platinum canoe through which a high current
was passed for heating. Heating the mixture in a quartz boat is inviting
unreliable data. Nearby quartz walls of the Sakai-Krouse reactor were
water-cooled to minimize oxygen exchange. Shakur's thesis describes a
built-in-house reactor with eight vertical electrodes in a horizontal
circular stainless steel base. Four platinum canoes are pinched into the top
of these electrodes. A viton gasket is used between the SS base and a "hat"
made with a SS flat ring and SS beaker. There is a water coil on the hat to
prevent potential warming of the viton gasket. There is a glass port in the
top of the hat (bottom of the beaker) for occasional measurement of the
reactor temperature with an optical pyrometer. We tried to publish a
description of this reactor once but one referee thought that it was not
radically different from the reactor described by Sakai and Krouse.
C.E. Rees and B. Holt discussed analyses of O-isotopes in sulfate in a
chapter in H. R.Krouse and V.A. Grinenko, Eds,
(1991) "Stable Isotopes in the Assessment of Natural and Anthropogenic
Sulphur", John Wiley & Sons Ltd, 440 pp.
----- Original Message -----
From: "Stan Halas" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, November 30, 2004 1:51 AM
Subject: Re: sulfate 18O
> You may find the idea in Holt & Engelkeimer (1970) Anal. Chem. 42,
> and perhaps also in vol.1 edited by Pier de Groot.
> The method bases on reliable delta-66 and delta-50 measurements in SO2
> prepared by thermal decomposition of BaSO4. However in my opinion it is
> hard to avoid oxygen isotope exchange with nearly soft quartz (T=1500oC)
> used for reactor. The expected precision is ca. 10 times lower than in CO2
> Perhaps Roy Krouse will add a comment.
> Greetings to All,
> At 19:16 04-11-29 -0800, you wrote:
> >Is anyone familiar with the sulfate 18O analysis technique of Van
> >and Krouse? In the literature Ive found discussions about SiO2/V2O5
> >conversion to SO2. Im assuming the oxygens are all exchanged during this
> >reaction and this is the means to get the 34S number, but its unclear
> >the 18O numbers are coming from. Im assuming its graphite reduction to
> >or CO but I can not find that explicitly stated in any of the papers.
> >there any references to the 18O aspect other than Van Stepvoort's PhD
> >Greg Michalski
> >Stable Isotope Lab, 5108 Urey Hall
> >University of California, San Diego
> >9500 Gilman Dr.
> >La Jolla, Ca. 92093-0356
> Dr. Stanislaw Halas
> Mass Spectrometry Laboratory
> Institute of Physics, UMCS
> 20-031 Lublin, Poland
> phone: +48 81 537-62-75
> fax: +48 81 533-36-69